WO2008132147A1

WO2008132147A1 - A kiln and a method for curing tobacco leaves

Info

Publication number: WO2008132147A1
Application number: PCT/EP2008/055029
Authority: WO
Inventors: Sérgio Torres DA SILVA
Original assignee: Souza Cruz SA; British American Tobacco Investments Ltd IFI; British American Tobacco Co Ltd
Current assignee: Souza Cruz SA; British American Tobacco Investments Ltd IFI
Priority date: 2007-04-25
Filing date: 2008-04-24
Publication date: 2008-11-06
Anticipated expiration: 2009-10-25
Also published as: BRPI0702173A2

Abstract

The present invention relates to a kiln and a method for curing tobacco leaves wherein the flow of air (6, 7) within the kiln changes direction periodically, allowing the cure of loose tobacco leaves placed at random on tobacco leaf drying modules (2) in a substantially horizontal orientation.

Description

"A KILN AND A METHOD FOR CURING TOBACCO LEAVES" Field of the Invention

The present invention refers to a kiln and a method for curing tobacco leaves wherein the direction of the flow of air within the kiln is changed periodically, allowing to cure loose tobacco leaves randomly placed on tobacco leaves drying modules in a substantially horizontal position. Prior Art

In Brazilian patent No. MU7703261-6 there is disclosed a module for drying tobacco leaves wherein the tobacco leaves can be placed loosely thereon without requiring stitching or fastening to supporting rods as usually practiced in the prior art.

However, such drying module evidences a better performance when the tobacco leaves are supported on their stems, thereby assuming a substantially vertical orientation, whereby the air that flows around the tobacco leaves is provided the fullest possible contact with the surface of the tobacco leaves.

The disposition of the tobacco leaves in a substantially vertical orientation requires that the tobacco plant have a stem that stands out sufficiently from the body of the leaf to allow that the leaf be supported on the stem in the drying modules. Such requirement causes a problem in the case of oriental, Turkish or aromatic types of tobacco that do not have their stems standing out in relation to the leaf, and therefore cannot be supported in the substantially vertical orientation.

Therefore, in order to use the same loose leaves concept described in document No. MU7703261-6, the tobacco leaves of the oriental,

Turkish or aromatic types should be loosely disposed in a substantially horizontal orientation. However, such position hinders the air circulation across the leaves, and thereby jeopardizes the cure thereof.

The solution proposed for the cited prior art problem resides in the cure of the tobacco leaves by means of an alternating flow of air within the kiln. In this manner, a large part of the area of the tobacco leaf, even in the case where the latter is placed in the horizontal position, comes into contact with the air that circulates inside the kiln. Notwithstanding what has been set forth above, the present invention may also be used to cure tobacco leaves that are fastened by other means, since the variation of the air flow direction inside the kiln allows that a larger area of the tobacco leaf be involved by the flow of air. Summary of the Invention In a first aspect, the present invention relates to a kiln for curing tobacco leaves, comprising a structure, at least a supporting means for tobacco leaves, an air heating system and an air circulation system wherein the air circulation system comprises at least a fan that blows air into the kiln in an ascending direction when the fan rotates in one direction and blows the air into the kiln in a descending direction when the fan turns in an opposite direction.

In a second aspect, the present invention relates to a method for curing tobacco leaves, such method comprising the steps of placement of the tobacco leaves on supporting means and subsequent cure thereof, wherein the flow of air that passes across the leaves alternates between an upward motion and a downward motion, wherein the tobacco leaves are preferably accommodated loosely in the drying modules in a substantially horizontal position. Brief Description of the Figures In Figure 1 there is shown the drying module that constitutes the object of document No. MU7703261-6. in Figure 2 there is shown a side view of the kiln for curing tobacco leaves.

In Figure 3 there is shown a view of the inside of the tobacco leaves curing kiln, wherein the tobacco leaves are placed in a substantially vertical orientation.

In Figure 4 there is shown a view of the inside of the kiln for curing tobacco leaves, wherein the tobacco leaves are placed in a substantially horizontal orientation.

In Figure 5 there is shown a view of the inside of the kiln for curing tobacco leaves wherein are illustrated the ascending and descending flows of the air that circulates within the kiln.

In Figure 6 there is shown the air heating and circulation system of the kiln.

In Figure 7 there is shown the front part of the kiln, wherein there may be noted the kiln's air recycling system. Detailed Description of the Invention

The present invention refers to a kiln and a method for curing tobacco leaves, particularly for curing of loose leaves of tobacco of the oriental, Turkish or aromatic types. The kiln comprises a structure 1, usually made of masonry and which is provided with supporting means on its inner walls whereon are installed supports for tobacco leaves 2, preferably consisting in the module for drying loose leaves as taught in patent No. MU7703261-6. Such supports are positioned at least at one level inside the kiln.

The kiln further comprises a heating system 3 to heat the air that circulates inside the kiln. There is normally used a furnace made of masonry or a heat exchanging means as disclosed in document No. PI0301943-8, and in this regard it should be noted that the present invention is not restricted to any specific type of heat exchanger.

Furthermore, the kiln comprises an air circulation system 4 which, preferably by means of the fan 5 drives the air in forced circulation within the kiln. The air travels a path between the inside of the kiln, where it supplies heat to the tobacco leaves, and the heating system 3, wherefrom it is provided with the thermal energy provided by the heat exchanger.

To allow an improved drying of the tobacco leaves, particularly in the cases where the tobacco leaves are loosely laid on the drying modules as disclosed in document No. MU7703261-6, the fan 5 of the air circulation system 4 according to the present invention is capable of blowing air into the kiln in the ascending direction 6 when the fan turns in one direction and blowing the air in to the kiln in the descending direction 7 when the fan turns in the opposite direction. The said effect may be achieved, for example, by using a fan whereof one half of the fan blades are provided in a given orientation and the other half are provided in an inverse orientation.

In the preferred embodiment of the present invention, when the flow of air occurs upwards 6, the recycling air is admitted into the upper inlet means 8 and when the flow of air occurs downwards 7 the recycling air will be admitted into the lower inlet means 9. The recycling of air within the kiln provided by the inlet means 8 and 9 is intended for controlling the moisture content in the kiln, that is performed together with the exhaust means 10. The air with excessive moisture content is removed from within the kiln through the exhaust means 10 while the new air is admitted through the inlet means 8 or 9. Such control is usually performed based on the measurement of the dry and wet bulb temperatures within the kiln.

The tobacco leaves support means 2 may be positioned a tone or more levels, and may be provided over one another allowing sufficient space therebetween for storing the tobacco leaves. Figure 4 depicts an embodiment with three levels and Figure 3 depicts an embodiment with one sole level.

The present invention further relates to the method for curing tobacco leaves, the said method comprising the steps of placement of the tobacco leaves on tobacco leaves supporting means 2 and cure of the tobacco leaves, wherein the flow of air that crosses the leaves alternates periodically between an upward direction 6 and a downward direction 7.

The said method is preferably intended to be used for curing loose tobacco leaves that are accommodated on the drying modules as those disclosed in document No. MU7703261-6 in a substantially horizontal orientation, particularly with relation to oriental, Turkish or aromatic tobacco types that do not have a stem with sufficient length to allow the accommodation thereof in a substantially vertical orientation.

Meanwhile, the use of the method according to the present invention when the tobacco leaves are positioned in a substantially vertical orientation provides an improved effect on the cure of the tobacco leaves, since the circulation of air within the kiln is optimized. In the same manner, the method according to the present invention may be used with any type of fastening of tobacco plants, since the effect of the inversion of the air flow within the kiln optimizes the cure of the tobacco leaves, as a larger area of the tobacco leaf will be subjected to a heat exchange by forced convection with the hot air flow.

In the method according to the present invention the leaves may be laid down in the drying modules on top of one another. However, the greater is the amount of laid down leaves, the longer will be the time required for the cure thereof, which fact may compromise the quality of the cured tobacco leaf.

Claims

1. A kiln for curing tobacco leaves, comprising a structure (1), at least one supporting means for tobacco leaves (2) that may be provided at one or more levels inside the kiln, an air heating system (3) and an air circulation system (4), characterized in that the air circulation system (4) comprises at least one fan (5) which blows air into the kiln in an ascending direction (6) when the same rotates in one direction and blows the air into the kiln in a descending direction (7) when it rotates in an opposite direction.

2. A kiln, as claimed in claim 1, characterized in that the tobacco leaves supporting means is a module for drying loose leaves.

3. A kiln, as claimed in any one of claims 1 or 2, characterized by comprising a system for recycling the air present inside the kiln (8, 9, 10).

4. A kiln, as claimed in any one of claims 1 to 3, characterized in that the supporting means for the tobacco leaves (2) may be positioned over one another allowing sufficient clearance for storage of the tobacco leaves therebetween.

5. A kiln, as claimed in claim 4, characterized in that the supporting means for the tobacco leaves (2) are provided a tone or more levels.

6. A method for curing tobacco leaves, characterized by comprising the steps of: placing the tobacco leaves on the supporting means for tobacco leaves (2); curing the tobacco leaves, where the flow of air that passes across the leaves alternates periodically between an upward direction (6) and a downward direction (7).

7. A method, as claimed in claim 6, characterized in that the tobacco leaves supporting means is a module for drying loose leaves.

8. A method, as claimed in claim 7, characterized in that the tobacco leaves are accommodated in the drying modules in a substantially horizontal orientation.

9. A method, as claimed in any one of claims 6 to 8, characterized by additionally comprising the step of recycling of the air that circulates within the kiln.