EP0546986B1 - Expanding and drying of tobacco - Google Patents

Abstract

A method and an apparatus are described for the expanding and drying of tobacco by means of steam and/or hot gas, according to which method the tobacco is metered into the inner compartment (4), defined at least from two flat jets (3, 3') which flow into the channel from the opposing sources outside the channel walls and are guided into each other at an acute angle, and the tobacco, after the acceleration of speed by means of the flat jets, is deflected by means of a cross-flow, accelerated again, expanded and dried. <??>The device preferably consists of a partially rectangular metering channel section (A-A), which, farther on, is arranged with a gas-permeable channel segment (5) for extracting part of the treatment medium in the channel, the latter, at least in its last section, terminating with a vertical channel (8) connected thereto at 90 DEG , which is surrounded by a wider pipe (9) called a "tower". <IMAGE>

Description

In the effective expansion and / or drying of tobacco, optimal heat transfer plays an important role for good heat utilization and effectiveness. For this purpose, the increased relative speed between the gas-containing treatment medium and the solid as well as the sudden pressure drop from a higher pressure range to a lower range in various ways have been proposed in general.

Several patents describe the use of the increased relative speed to improve the drying and / or expansion of wet tobacco. For example, DE-PS 30 37 885 proposes deflecting devices which are offset opposite one another in a pneumatic transport pipe, in order thereby to change the direction of movement and the relative speed of the tobacco rib parts with respect to the gaseous heating and transport medium several times. However, these deflection devices lead to deposits of tobacco components on the walls of the pneumatic tube.

According to DE-OS 36 19 816 it is proposed that the hot tobacco should be separated from the steam or gas by means of a separator consisting of a sieve, which extends at an angle of 135 ° to 155 ° to the axis of the transport line at the downstream end thereof. An analogous proposal is described in DE-OS 36 19 815, with the difference that the tobacco drying device consists of two gas flow lines with two separators which are connected to one another, and each porous separator arranged at an oblique angle to one another should remove the tobacco from the gas separate. With this system, the tobacco should be accelerated twice by the gaseous medium.

The tobacco flowing at an oblique angle at high speed in the ascending direction can precipitate on the surface of the gas-permeable separators arranged at an angle to the flow direction or block it.

Flow changes in a pneumatic hot steam tobacco transport channel system lead to undesirable deposits in moist tobacco, especially if the tobacco moisture content is above 35%. These deposits occur to the greatest extent where the flow change is greatest, e.g. in the form of a pneumatic transport system. This is also the case with the method described in DE-OS 28 41 874. According to a later patent specification of the same method, the deposit should be reduced by cooling or condensation on the sheet.

DE-PS 38 39 529 describes a method and device for the expansion of cut tobacco material, according to which a tobacco carrier gas stream is encased by a separately supplied gas stream, thereby reducing the relative speed to increase between the tobacco material and the gas flow several times, but this is insufficient due to the coating of the tobacco material caused above by the carrier gas and is not effected over the entire channel cross section. The additional gas stream is supplied via a plurality of slots which are formed at an acute angle as an opening in the channel jacket in the direction of flow.

The further treatment of the tobacco after its exit from the treatment channel is only shown schematically, without describing or claiming the type of treatment or drying. No redirection of the flow direction is reported.

According to DE-PS 33 15 274, a tobacco gas mixture flows from a horizontal transport channel through a narrow nozzle at very high speed into a dryer tube provided with bends. In order to be able to move the tobacco further, the flow rate of the hot gas in the drying tube must be somewhat higher than that of the tobacco gas mixture emerging from the nozzle. This requires an uneconomically high amount of hot gas and involves intensive mixing or dilution of the tobacco with the gas.

When tobacco suddenly enters the hot air environment from the nozzle, the heat transfer caused by the turbulence can cause an expansion of the tobacco, mainly in the more expandable tobacco fins. For a more significant expansion of tobacco lamina, however, the conditions described in the above patents are not sufficient to produce the desired expansion effect.

In the publication DE-OS 26 37 124 is the use a venturi nozzle or a reduction in cross-section of the tobacco transport channel is described in order to increase the relative speed between the hot gas-containing medium and the tobacco and thus the expansion effect. The expansion effect can of course be further improved by narrowing the cross-section of the tobacco transport channel or by using a venturi nozzle for tobacco with a higher moisture content. The patent EP 074 059 is practically based on the same principle. Here it is additionally claimed that the tobacco material should be metered and conveyed in the "base" of a free jet or nozzle. This could be ensured, inter alia, that the tobacco metering is directed directly at the opening of the nozzle, as can be seen from FIGS. 3, 4, 5. The supply of the tobacco or its transportation in the "base point" of a nozzle is practically not feasible, since the jet flowing out of the nozzle has such a high speed that it cannot take in the tobacco at this point. It is only after the jet has spread and fills the transport channel that there is a possibility that the tobacco will be embedded in the jet and transported with it. At this point, however, the cross-section of the beam reduces its speed and temperature. In this sense, an optimal use of the heat transfer, which is necessary for a good ex expansion effect for cut leaf tobacco, is reduced.

According to DE-PS 31 47 846, which is equivalent to this patent, the tobacco should be accelerated in the expansion zone and transported by an approximately constant speed, then decelerated in a divergent flow under pressure increase. This design can be achieved by temporarily narrowing the channel cross-section, as in Fig.1 of this document can be guaranteed. Speed acceleration and reduction of a tobacco-vapor mixture is described in the previously cited DE-OS 26 37 124 by using a venturi nozzle and in "PS dispersion dryer" cited in DE-PS 22 53 882, but these statements can be made due to the limited possibility of tapering Canal cross section and mechanical abrasion of the tobacco through the channel wall are not considered to be optimal.

It has now been shown that an improvement in the tobacco feed metering and special flow velocity conditions of the tobacco gas stream, as well as a special type of deflection by cross flow, can result in an additional improvement in effectiveness.

The aim of the invention is to improve the expansion effect and the drying and to do this without the use of gases or liquefied gases under excess pressure only by using water vapor and / or air in a simple device in the atmospheric range.

This goal is achieved according to the invention by means of a method according to claim 1. Appropriate further developments of the method according to the invention are the subject of claims 2 to 11. The subject of the invention is also a device for carrying out the method of the invention according to claim 12.

The invention is explained below with reference to the drawing, for example. Show it:
1 and 2 schematically show two examples of embodiments of devices according to the invention for carrying out the method according to the invention; Figure 3 is a section along the line III-III in Figures 1 and 2. Figure 4 is a section along the line IV-IV in Figures 1 and 2. Fig. 5 different views of those in Figs. 1 and 2 used flat nozzles, and Fig. 6 shows another arrangement of the flat nozzles and the metering of the tobacco material.

According to the proposed method, the tobacco is supplied from a metering device 1 into a channel section with the same diameter after loosening or separating the tobacco fibers, which can be done by using known vibrators and / or needle rollers. This is of particular advantage in the case of sliced leaf tobacco known as "lamina". If you want to put the tobacco in a steam jet and this jet emerges from a nozzle at high speed, the difficulty can arise that the tobacco penetrates into the barely unevenly or not at all despite the suction effect of the jet.

According to the invention, it has now been shown that optimal and gentle treatment of the tobacco is made possible if it is made of steam from the laterally widespread surfaces of the tobacco flowing in from two opposite nozzle openings at an angle of 5 ° to 60 ° to the channel axis and / or hot gas, in the direction of flow intersecting flat jets 3, 3 'laterally delimited interior 4 is metered, transported with this medium at high speed and the latter is increased again at least by changing the direction of flow once by cross-flow by means of a separate gas stream.

The flow velocity of the flat jets 3,3 'enclosing the tobacco from two sides, which preferably flow into the channel 15 from each outside of the flat sides of a rectangular channel wall 15, one flat jet nozzle 2,2' flows into the channel 15 at the tobacco receiving point of the jets up to its point Crossing point between 300, m / sec. and 1OOm / sec. In this case, the tobacco from the vapor / gas jet surface carrying it is not touched mixed with the channel wall in the beam, but at the meeting point of the two directed beams. This significantly reduces the mechanical abrasion or the risk of damage to the tobacco particles and exposes the tobacco to an additional acceleration.

In a preferred embodiment of the method mentioned, the tobacco can be metered into a vertical channel section 15. The tobacco is preferably metered through the upper opening of a vertical rectangular channel section 15, the tobacco falling onto the laterally widening surfaces of vapor-containing "carpets" 4,4 'which preferably flow out from opposite openings of preferably one flat nozzle 2, 2' each is accelerated. Furthermore, the tobacco is additionally accelerated at the intersection of the two flat jets 3, 3 ', and then its flow rate is slowed down by withdrawing part of the transporting steam. This takes place on a section of the transport channel, which is designed as a gas-permeable channel section 5, through which part of the steam can flow out. The steam can be removed through the jacket 6 surrounding this channel section 5 or preferably returned to the system after overheating.

The reduction in the flow rate due to steam extraction can then additionally be effected by widening the channel cross section. The tobacco-steam and / or hot gas mixture emerges from the vertical channel section 16 at a speed of 3 m / sec. up to 1Om / sec. and is in a horizontal channel section 7 by means of a separate hot gas stream 13 at a speed of 11 m / sec. up to 60 m / sec. deflected by cross flow. This flow containing tobacco can be diverted from the horizontal channel section 7 into a vertical channel section 8 by a further redirection by means of a separate gas stream 14 at a higher speed than that used in the horizontal channel section 7 and thereby accelerated again. The tobacco can also be transported without a cross flow over an arc in an extended vertical channel section 8. The vertical channel section 8 is surrounded by a tube 9 with an enlarged cross section to form a tobacco separation zone. After exiting the channel section 8, the tobacco is deflected into the interior 17 surrounding it by the air resistance and leaves this interior 17 after expansion and drying by gravitation downwards.

Another possible embodiment is that the tobacco is dosed into a horizontal through a vertical channel. In this case, the two flat jets 3, 3 '' must flow out of openings which are arranged on opposite sides but are offset from one another. The different distance of the two flat jets 3.3 ″ from the respective nozzle openings to their intersection would cause the two flat jets to have an uneven speed. To avoid this, the diameter of the individual nozzle openings and the vapor pressures in front of the nozzles would have to be adapted to these requirements.

The use of two flat jets, which surround the tobacco from two opposite sides and mix with it at their cross point, also has the advantage over the use of round jets that the flat jets spread mainly laterally during their flow and not in theirs Overall cross-section, increasing their speed with distance decreases less from the nozzle opening. Due to the negative pressure prevailing in the channel system due to the high flow velocity, the tobacco metered in is deflected from the nozzle opening and falls onto the widening surface of the flat jet. It is advantageous to use only one flat jet each with wider nozzle openings and to position them outside the channel wall. So the tobacco falls with greater certainty on the surface of the laterally spreading steam jets.

In order to further improve the expansion effect, which already arises in the described manner of metering in the tobacco from at least one jet consisting of steam and / or hot gas, the deflection of the tobacco-steam mixture by transverse flow 13 or 14 is proposed according to the invention.

It has been found that when a cross-directional flow 13 or 14 penetrates into a jet consisting of crushed tobacco and steam and / or hot gas and the tobacco-containing jet is deflected, the heat transfer from gas to tobacco and thus also the drying and Expansion effect significantly improved. In this case, several components of action together lead to the improved effect. The cross flow is dammed up in front of the jet containing solids and therefore a pressure gradient is built up transversely to its direction of propagation. It can be assumed that the surprisingly high effect achieved in the practical tests according to the invention is achieved by the interaction of the two components: pressure build-up or drop in cross flow together with the difference in transport speed between gas and tobacco.

By the way of the deflection according to the invention by cross-flow of the jet containing the tobacco and the transport medium together with the increase in flow speed according to the invention when tobacco is fed and during the deceleration before the deflection, the expansion and drying effect could be significantly improved compared to the previously known solutions. According to the invention, the deflection from horizontal to vertical or from vertical to horizontal direction can take place. A triple redirection can also be used. For example, if the tobacco transport medium mixture is diverted from vertical to horizontal and from there again to the vertical direction.

When the gas-solid mixture flowing out of a horizontal channel section 7 is deflected upward by an auxiliary jet 14, the auxiliary jet has to overcome the resistance caused by the weight of the tobacco (gravitation), as a result of which it is deflected before the horizontal jet is deflected in the connecting space between the horizontal and vertical channels is subjected to a congestion effect and then to a greater pressure drop. The relaxation time, i.e. the time it takes for the tobacco particles to adjust to the new flow direction is also greater in this case, as a result of which the effect of the heat transfer is additionally improved.

The use of a gas-permeable channel section 5 in the horizontal channel section 7 enables a part to be removed from the transport medium, which can be returned to the system, and at the same time reduces the flow velocity of the jet. This not only prevents an adverse impact of the solid on the wall of the vertical channel section 8, it also achieves an economic advantage. The The amount of gas and / or steam required for the additional acceleration can namely be reduced and the diameter of the horizontal and vertical channel sections can be kept approximately the same.

The section length and the porosity of this channel section is selected such that, for a given tobacco gas flow rate, there is no lateral deviation of the flow bundle and, accordingly, no deposition or blockage on the porous surfaces of this porous channel section 5.

In the original tobacco-transporting steam and / or hot gas stream, the tobacco-steam-weight ratio is between 1: 0, 7 and 1: 4. The weight ratio between the first tobacco-transporting treatment medium 4,4 'and the deflecting treatment medium 13 or 14 in the deflection zone is between 1: 1 and 1: 2.

In the last phase, the tobacco preferably arrives after the corresponding deflection from the channel section 8 into a pipe or a "tower" 9 with a larger diameter than that of the channel section 8. In order to further reduce the flow velocity in the second channel, the cross section at the outlet end of the Channel section 8 are expanded. The free space above the centrally arranged channel section 8 is dimensioned such that the tobacco exiting into the wider pipe 9 is slowed down by the air resistance and its direction of flow changes due to its gravity. The tobacco will fall freely between the outer channel wall 8 and the inner so-called "tower" wall 9 after changing its flow direction by 180 ° onto a conveyor belt and transported away with the desired degree of dryness.

The tobacco falling down in the tube between the outer wall of the relatively short vertical channel section 8 and the inner wall of the tube 9, which surrounds it at a distance, can be exposed to an extended residence time by an additional dry gas, preferably hot gas, which slowly flows in from bottom to top.

The inflow rate of a separate gas, which slowly flows upwards from the bottom of the tower in counterflow to the tobacco falling down, should be the rate of 1 m / sec. if possible do not exceed.

This counterflow should be set in such a way that there is no material jam and the tobacco can leave the drying tower by gravitation.

Due to the repeated increase in relative speed and the change in flow direction, the heat transfer and the energy utilization are significantly improved, whereby extremely economical drying, expansion or removal of the undesirable volatile substances can be achieved.

In the event of a more intensive drying requirement, two treatment units, in particular two so-called tower systems, in which the drying mainly takes place, can be connected in succession.

As can be seen from the drawing, the device consists of a tobacco feed channel, from which the tobacco is metered and loosened through a lock 1 and preferably subsequently by a needle roller in a vertical, rectangular transport channel section 15. Outside the opposite flat channel walls (section III-III) Above, a wide flat nozzle 2, 2 'is arranged directly after the metering device, from which two flat, carpet-like, laterally widespread flat jets 3, 3' consisting of steam and / or hot gas flow downward and intersect at an acute angle in the direction of tobacco flow. The tobacco falls into the interior 4, which is formed by the two flat jets 3, 3 'consisting of steam or hot gas, onto the laterally widening flat jets which accelerate and transport the tobacco in a flash. To reduce the speed of the tobacco and the steam and / or hot gas, gas-permeable channel section 5 can be provided in the further course, preferably in the round channel section 16, through which part of the steam escapes into a double jacket 6 and is returned to the system. (Not shown in the drawing).

The channel can be extended in the horizontal direction 7 by an arch (FIG. 1). A better or more effective solution is if the vertical channel section opens directly into a horizontal pipe 7 (see FIG. 2) and the tobacco is exposed to separate hot gas for deflection by cross flow. The horizontal channel 7 can also be provided with a gas-permeable channel section 5, analogously to that described above. After the flow velocity has been reduced, the tobacco can be redirected again into a vertical channel section 8 and, in a wider pipe 9 surrounding it, a so-called “tower”, can change its direction of flow through the air resistance or downward due to gravity. The steam-containing hot gas flowing out upwards by means of the suction fan 11 is separated by the sieve 10 ′ from the tobacco falling downward by gravity and leaves the space between the outer wall of the vertical channel section 8 and the expanded tube 9, or "tower" down through the opening 12.

example 1

Sliced Burley tobacco with a moisture content of 27% is arranged after loosening with a needle roller through a lock 1 in the vertical, rectangular duct 15 of the duct walls in an opposing position, two flat jet nozzles 2, from which steam with a temperature of 220-250 ° C. flows in. The tobacco is diverted upward from the horizontal channel section 7 by means of an auxiliary gas stream 14 at a temperature of 140 ° C - 180 ° C. The tobacco leaves the outlet opening 12 of the "tower" dried and expands downward. The temperature and flow rate of the gas flowing up the channel is regulated so that the tobacco leaves the "tower" with a moisture content of 11.5%.

The untreated tobacco and the expanded tobacco are adjusted to 12% moisture after conditioning.

The filling capacity of the tobacco was measured in a Brogwaldt densimeter (20 g tobacco was loaded in a cylinder with 6 cm O with a weight of 3 kg for 30 seconds and the height of the tobacco column was measured after the pressure was released. Height of the tobacco column Untreated Expanded Filling capacity increase 33.83mm 50.80mm 50%

Example 2

Virginia cut tobacco was treated as in Example 1. Height of the tobacco column Untreated Expanded Filling capacity increase 28.93 mm 57.47mm 1OO%

Claims (12)

1. A process for expanding and drying tobacco by means of vapor and/or hot gas, wherein the moist tobacco is metered into an interior space (4) which is delimited by at least two flat jets (3,3') comprising vapor and/or hot gas, these flat jets being directed towards one another at an acute angle and consequently sudenly taking up and accelerating the tobacco to be treated, then the transporting velocity being reduced by the removal of vapor, and subsequently the expanded tobacco being supplied to fixing and drying.
2. A process as claimed in claim 1, wherein the flow velocity of the tobacco is accelerated by the flat jets and if appropriate by deflection by means of transverse flow, and is reduced at least once by the removal of vapor from a section (5) of the transporting channel.
3. A process as claimed in the claims 1-2, wherein the flat jets (3,3') flow into the transporting channel from flat jet nozzles (2,2') which are arranged in or outside opposing channel wall regions and are directed towards the channel axis at an angle of 5-60°.
4. A process as claimed in the claims 1-3, wherein the tobacco is supplied into the interior space resp. onto the flat jets delimiting the latter in the manner of a trapesium on their laterally widening surface, and the tobacco and the vapor- and/or hot gas-containing medium are transported in an at least partially rectangular channel.
5. A process as claimed in the claims 1-4, wherein, to reduce the flow velocity, vapor is removed through at least one gas-permeable section (6) of the channel (7).
6. A process as claimed in the claims 1-5, wherein the transverse flow of the tobacco is effected in a channel system by deflecting the flow direction from the vertical to the horizontal direction and from there upward into a vertical channel section (8) connected thereto, in each case by a separate hot gas-containing medium.
7. A process as claimed in one or more of the preceeding claims, wherein the flow velocity of the flat jets which flow in the channel from its opposing sides thereinto is, on contact with the tobacco, between 100 m/sec. and 300 m/sec. and, on their introduction to the chance in direction of flow by transverse flow into a second channel section (7) connected to the first channel section at a 90° angle, between 3 m/sec. and 10 m/sec.
8. A process as claimed in one or more of the preceeding claims, wherein the flow velocity of the tobacco-containing vapor and/or hot gas stream is between 10 m/sec. and 60 m/sec. after deflection by means of a separate gas-containing stream (13) in the second channel section (7).
9. A process as claimed in one or more of the preceeding claims, wherein the tobacco/vapor and/or gas mixture is subjected to a number of deflections, the last change in the direction of flow being from a horizontal channel section to a vertical channel (8) connected thereto by means of an additionally introduced gas stream in that the vertical channel section (8) opens upward into a pipe (9) having a widened diameter, and the tobacco emerging from the vertical channel section (8) emerges downward between the latter (8) and the pipe (9) surrounding the latter from this pipe (9) by gravity.
10. A process as claimed in one or more of the preceeding claims, wherein the transporting medium, comprising vapor and/or hot gas, has a temperature between 180° and 300°C after taking up the tobacco.
11. A process as claimed in one or more of the preceeding claims, wherein the comminuted tobacco comprises out comminuted tobacco lengths and/or lamina or tobacco film.
12. An apparatus for carrying out the process as claimed in the claims 1-10, wherein the apparatus comprises at least a tobacco-metering sluice gate (1), a rectangular expansion channel section (15) which is connected thereto, extends vertically downward and in which a respective blanket-like vapor-containing flat jet (3,3') flows in through flat nozzles (2,2') arranged in or outside the channel walls opposite one another, and the two flat jets intersecting one another at an acute angle take up tobacco in the interior space (4) delimited thereby, the transporting channel continues from the vertical to the horizontal direction (7), the vertical and/or horizontal channel section being provided with a gas-permeable section (5), the horizontal channel section (7) opening into a separate vertical channel section (8) which is surrounded by a pipe (9) having a larger internal cross-section, and from this the tobacco emerging downward (12) in the expanded and dried state and the vapor- and/or hot gas-containing medium emerging upward through a screen (10) by means of suction removal (11).

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