EP1983850B1

EP1983850B1 - Rotary dryer for leaf, strip or shredded tobacco

Info

Publication number: EP1983850B1
Application number: EP06807227A
Authority: EP
Inventors: Mario Martin
Original assignee: Comas SpA
Current assignee: Comas SpA
Priority date: 2005-10-17
Filing date: 2006-10-12
Publication date: 2010-12-15
Anticipated expiration: 2026-10-12
Also published as: EP1983850A1; ATE491353T1; ITVE20050051A1; WO2007045606A1; PL1983850T3; DE602006019001D1

Abstract

A rotary dryer for shredded tobacco comprising a rotating cylindrical chamber (2), closed at it s two ends by two endpieces (4, 4') and provided along its entire length with a plurality of longitudinal fins (12) projecting into the interior of said chamber (2), for the tobacco to be dried a loading system connected to one (4) of the two endpieces, and for the dried tobacco a discharge system (10) connected to the opposite endpiece (4'), characterised by comprising inside the chamber an internal conduit (14) communicating with a hot fluid infeed conduit (16) provided in its cylindrical surface with a plurality of hot fluid passage apertures (18) defining with the inner wall of said drying chamber (2) a tubular chamber for treatment of the tobacco by said hot fluid, which traverses it in a substantially radial direction and leaves from both said endpieces (4, 4').

Description

The present invention relates to a rotary dryer for leaf, strip or shredded tobacco.
Rotary dryers for shredded tobacco are known. They comprise a cylindrical chamber closed at its ends by two endpieces, to which a hot air entry conduit and a hot air exit conduit are connected respectively. Two systems, for feeding the tobacco to be dried and for discharging the dried tobacco respectively, are also connected to said endpieces.
The inner surface of the cylindrical chamber comprises a plurality of longitudinal fins.
During operation the shredded tobacco to be dried is fed into the drying chamber via the feed system. Here it is heated by the chamber wall, itself heated by a vapour jacket or by direct flame, and at the same time is subjected to the flow of the hot drying air, which can circulate within the chamber in co-current or counter-current flow, depending on the direction in which the fluid is fed thereinto.
A drawback of said dryer is that the efficiency of the drying process is fairly low, in that the hot air flow has to pass through the entire drying chamber, and for evident practical reasons cannot have too high a velocity. Consequently the slow rate of the drying air is modest and the process efficiency is likewise modest.
DE 2436139 A1 discloses a rotary dryer for tobacco comprising a rotating cylindrical chamber closed at its ends by two endpieces and provided along its entire length with a plurality of longitudinal fins projecting into the interior of the chamber, a tobacco loading system and a tobacco discharge system, the dryer comprising an internal conduit communicating with a hot fluid infeed conduit and provided in its cylindrical surface with a plurality of passage apertures defining with the inner wall of said drying chamber a tubular chamber for treatment of the tobacco by said fluid,
According to the invention a rotary dryer for tobacco is provided as described in claim 1.
A preferred embodiment of the present invention is further clarified hereinafter with reference to the accompanying drawings, in which:

Figure 1: is a longitudinal schematic section through a rotary dryer according to the invention,
Figure 2: shows a variant thereof, and
Figure 3: is a partial cross-section on the line III-III of Figure 1.

As can be seen from the figures, the tobacco dryer of the invention comprises a cylindrical chamber 2 closed at its ends by two endpieces 4, 4' to which two exit conduits 6, 6' are connected for a hot drying fluid, which can be hot air or hot air mixed with hot vapour and/or steam.
A loading system 8 is also connected to the endpiece 4 to feed the tobacco to be treated, which can be tobacco in leaf, shredded or strip form, into the chamber 2, a discharge system 10 for the treated tobacco being connected to the endpiece 4'.
The drying chamber 2 is provided with traditional means for its rotation, not shown in the drawings, and is also provided along its entire length with a plurality of longitudinal fins 12 welded to its inner lateral surface and projecting towards the chamber interior. They are of slightly concave shape, with their concavity facing the direction of rotation of the chamber 2, in order to better mix the tobacco within said chamber during its rotation.
Inside the drying chamber 2 a pipe 14 is provided extending from one endpiece 4 to the other 4' and prolonging to the outside via a conduit 16 for entry of the hot drying fluid.
This pipe is provided along its entire lateral surface with a plurality of apertures 18 to which tubes substantially perpendicular to the cylindrical surface of the pipe are applied.
According to the invention, the pipe 14 is rigid with the cylinder 2 and rotate with it; depending on design choices, in other embodiments the pipe can be independent of the cylinder and remain at rest during its rotation, or rotate at a different speed.
The cross-section of the hot fluid infeed conduit 16 is greater than the sum of the cross-sections of the apertures 18 of the pipe 14, so that this is able to form a plenum chamber, i.e. is filled with fluid under pressure when working normally.
It can consist of a single tubular element or of two coaxial portions 14, 21 through which fluids can be fed at different temperatures via conduits 22, 23. Correspondingly, the two portions of the chamber 2 corresponding to the two separate coaxial tube portions are traversed by fluids at different temperature.
The chamber 2 is mounted on adjustable structures (not shown in the drawings), able to maintain the chamber 2 with its axis horizontal or inclined by the desired angle.
From the aforegoing it is apparent that the rotary dryer of the invention is particularly advantageous compared with traditional dryers, and in particular:

it enables all the tobacco to be dried with a fluid of constant characteristics and hence with high efficiency, and with a likewise high quality of the treated tobacco,
it uses a greater quantity of fluid than that used by traditional dryers of equal dimensions, as the flow of drying fluid leaves from both endpieces of the drying chamber,
it can use fluids at different temperatures in the drying chamber via concentric tubes,
it enables the inclination of the drying chamber to be adjusted, to hence regulate the conditions under which the tobacco is treated.

Claims

Rotatable dryer for cut tobacco comprising:
- a drying chamber delimited by a rotating cylindrical shell (2), shut on the two ends by two endpieces (4, 4'), and interested on all its length by a plurality of longitudinal ribbing (12) extending from said cylindrical shell inwardly to the drying chamber,

- a loading system (8) of the tobacco to be dried, connected to one (4) of the two endpieces,

- a discharge system (10) of dried tobacco connected to the opposing endpiece (4'),

- an inner pipe (14, 21) communicating with an infeed conduit (16) into a drying chamber of a hot fluid, said pipe being provided on its lateral surface with plurality of apertures (18) for the passage of the hot fluid, characterized in that said inner pipe (14, 21):

- is coaxial with said rotating cylindrical shell (2),

- is integral during rotation to said rotating cylindrical shell (2),

- is provided on the inner surface, in correspondence to each aperture (18), with a substantially radial tube (20),

- delimits with said rotating cylindrical shell (2) a rotating tubular drying chamber of the tobacco to be dried, which is crossed substantially in radial direction by the hot fluid pouring into said chamber through said tubes (20) and said apertures (18), and it leaves from both said endpieces (4, 4').
Dryer according to claim 1 characterized in that said infeed conduit (16) of hot fluid is connected with a source of hot air.
Dryer according to claim 1 characterized in that said infeed conduit (16) of hot fluid is connected to a source of hot air mixed to hot vapour.
Dryer according to claim 1 characterized in that the section of the infeed conduits (16) of hot fluids is greater than the sum of the section of the apertures (18) of the inner conduit (14).
Dryer according to claim 1 characterized in that said inner conduit is constituted by two coaxial tracts (14, 21), fed by means of two external infeed conduits (22, 23) of hot fluids bearing different temperatures and involving two distinct portions of said drying chamber.