BG63705B1 - Method and device for tobacco cooling and drying - Google Patents

Abstract

The method includes full and even drying and cooling of the tobacco, continuously through the entire tobacco layer getting across the drier (38) and the cooler (32). The device consists of multiple individually controlled heating zones with fluidized bed (22) 0) for drying the tobacco. An additional cooling zone with fluidized bed (32) cools the tobacco before its secondary wetting. A infinite conveyor (14) is spread over the heating and cooling zones. A vibration conveyor (60) feeds the dried tobacco across a steam tunnel (40) where the moisture content is increased to preset levels. 22 claims, 5 figures

Description

(54) TOBACCO DRYING AND COOLING METHOD AND APPARATUS

Technical field

The invention relates to a method and apparatus for drying and cooling tobacco, in particular by rapidly drying, cooling and re-humidifying sliced tobacco.

BACKGROUND OF THE INVENTION

The re-drying of tobacco leaf material is common in the processing of tobacco material, especially in the case of braille tobacco, before being processed into cigarettes and in the processing of heavy sinewy material. When the tobacco leaf material is dried again, the control of the moisture content of the tobacco is obligatory because of the strictness of the requirements for the specific moisture content of the tobacco leaf required for further processing. The processing of tobacco material, including drying, is preferably carried out at high speeds in order to keep production costs low and to reduce the processing space required in processing plants to a minimum. Thus, each stage of the processing of the tobacco leaf material requires the tobacco to be kept at a constant moisture content. Additionally, the weather, temperatures and humidity of the tobacco material drying affect the chemical composition and taste of the material being processed. Before drying, cut tobacco typically has a moisture content of about 30%. After drying, the moisture content can reach 5% and the tobacco becomes very fragile, which can cause the tobacco leaves to break during further processing. Fracture is particularly pronounced when the tobacco leaf after drying has a moisture content of about 5%. And since the chemical composition of the leaf and its inherent taste remain optimal, the moisture content after drying should be controlled to an ideal content of approximately 5%. This rigorous control of the moisture content must be carried out with as little refraction and fluctuations in the moisture content and chemical composition as possible. The breaking or breaking of the tobacco leaf is reduced by adding moisture to the leaf material during the re-wetting step. Re-humidifying the tobacco leaf or conditioning increases the moisture content of the tobacco material by up to about 15% so that the tobacco leaf can be further processed without further degradation and maintained at an optimum moisture content for further processing. Re-humidification is usually accomplished with reclamation water, steam, or both, by stirring the tobacco in a rotating cylinder. This often leads to further damage to the tobacco product. Therefore, the method and apparatus for drying, cooling and re-humidifying the tobacco material are very important.

Typically, sliced tobacco is dried using a jacket dryer. It blows the air below from the conveyors over which the tobacco is placed, by venting the drying air from above the tobacco product. It is known from US 3 224 452 that three zones are used in the oven casing, the purpose being to equalize the pressure in each zone, using sensory pressure means in at least two zones. The pressure in the zones is leveled using jet valves, but the solution is not effective in providing a high-speed treatment apparatus.

Alternatively, some dryers may include air-blown drying areas on top of the drying zone through the tobacco material and conveyor apparatus and venting through the bottom of the dryer. Generally, conveyor means use diffusion plates to align the air flow transversely to the conveyor with a casing in the upper drawing areas. Dryers of this type exhibit variations in humidity and therefore the tobacco processed in them is susceptible to changes in taste and quality.

In addition, the rate at which drying and re-moistening are carried out directly affects the cost and chemical composition of the processed tobacco. Typically, the tobacco is dried, cooled and re-moistened before being used in the cigarette production process within the range of 20 to 40 minutes. The time required to condition the material is long because, upon drying, the tobacco is treated by passing it through a curved path of the air stream, turning it over the air stream, or the tobacco being passed over pressurized air jets. Passing tobacco through a curved airflow path causes hygiene problems, obstruction problems, as well as other airflow path problems that often need to be addressed.

The leakage of tobacco over pressurized air jets causes large variations in the drying of the tobacco layer. Such variability creates problems in processing further down the production line, as some parts of the tobacco have been maintained at an appropriate temperature while other parts have not. Additionally, the chemical composition of tobacco may be different because it has been dried to different moisture contents. So it takes a long time to dry the tobacco material properly.

Additional problems are related to the re-humidification of tobacco. If the moisture applied to the tobacco is only applied to spherical points, some areas of the tobacco layer have a higher moisture content than others, which changes the characteristics of the tobacco. Therefore, drying and re-humidifying the tobacco without major differences in two different samples is required, as well as keeping the processing time to a minimum.

In particular, the drying of the tobacco material directly affects the release of pyrazines into the tobacco. Attempts to change the drying process in terms of speed and temperature of drying can affect the level of pyrazines in tobacco, thereby affecting the essential sides of the material being processed, such as taste and aroma. Therefore, any change in the drying process should not change the composition of the tobacco as it relates to pyrazines and other constituents.

SUMMARY OF THE INVENTION

The invention relates to a method for drying, cooling and re-humidifying with a short residence time of the cut tobacco material with minimal destruction of the tobacco during processing. The invention provides evenly distributed drying and humidification throughout the layer of processed tobacco material, as well as reducing the time for complete completion of drying, cooling and re-humidification of the tobacco. The invention also provides means for rapid drying and re-humidification of large quantities of tobacco, which are processed in a short time and on a very small floor area, while minimizing the damage from tobacco processing. As a result, the total residence time is about 10% of the drying time required by known technologies.

The method consists of loading tobacco onto a conveyor belt with a predetermined layer thickness. The tobacco thus placed is transferred through an oven with heated air and then through a cooler. Subsequently, the humidification of the tobacco is also carried out.

According to the invention, the transfer of the tobacco to the dryer further includes supplying air heated to a first pre-selected temperature in the first heating zone for drying and creating a fluidized bed, recirculating the air in the first heating zone, supplying air heated to a second pre-selected temperature, in a plurality of heating zones, following on from the first heating zone, the recirculation of air in the plurality of descending heating zones, such as the air temperature in each zone is in the range of 93.3 ° C (200 ° F) - 137.8 'C (280 ° F), raising the temperature of the tobacco to the same limits and reducing its moisture content to about 5%. The tobacco is transported by belt conveyor to a cooler operating in a fluidized bed with atmospheric air, the tobacco is transferred to a humidifying tunnel, operating with a vibrating conveyor and moistened into a humidifying tunnel.

The short-term tobacco drying apparatus consists of a drying unit consisting of a plurality of independently controlled zones. According to the invention, a cooling unit with a cooling zone, a belt conveyor passing through the dryer and the cooling unit is also provided to the unit. At the end of the belt conveyor is a transitional zone with a vapor layer, a humidifier, as well as a humidifier containing a steam tunnel and a vibrating conveyor. The latter connects the previous zone with the vapor layer and the outlet of the humidifier. The drying unit includes first, second, third, fourth and fifth heating zones ventilated with air heated from 93.3 ° C (200-F) to 137.8 ° C (280 ° F).

Description of the attached figures

The invention is illustrated by the accompanying figures, of which:

Figure 1 is an exemplary depiction of an apparatus for drying, cooling and re-humidifying a tobacco;

Figure 2 is a block diagram illustrating operation, comprising drying, cooling and re-humidifying with a short residence time;

Figure 3 is a front view of a fluidized bed showing the air directed at the processed tobacco; 5 Figure 4 is a perspective view of the re-humidifier;

Figure 5 is a diagram representing the formation of pyrazines in tobacco during drying.

Examples of carrying out the invention

A preferred embodiment of apparatus 10 of the invention for drying, cooling and re-humidifying with a short residence time of sliced tobacco is shown in Figure 1. The sliced tobacco 12 is fed from the hopper, not shown, to the conveyor belt 14. The tobacco 12 is fed to the tape 14 with a constant thickness of about 7.62 cm (3 inches) along the entire cross section of the tape 14. The tape 14 moves the tobacco through each of the heated areas of the dryer 38, which zones are designated as Zone 1, Zone 2, Zone 3, Zone 4 and Zone 5, respectively designated as 22, 24, 26, 28 and 30. The dryer 38 consists of separate, independently controlled heating zones so that the tobacco can be precisely processed and the drying can be finely controlled Fr. Each zone can be controlled independently, which includes temperature, pressure and exhaust air flow. Each zone of the drying process dries tobacco 12 using known fluid bed technology. An example of such a dryer is the Jetzone Fluid Bed unit manufactured by Wolverine Corporation. Each of the zones 22, 24, 26, 28 and 30 is independently controlled and has a separate inlet for the heated air and an outlet for the exhaust, as shown in Fig. 1. After drying, the tobacco 12 is fed into a cooler 32, where the fluid bed technology is also applied. The tobacco 12 is cooled using ambient air to reduce its temperature for proper re-humidification. From the cooler 32, the tobacco 12 moves from the strip 12 to the steam / water layer 36, which absorbs evenly distributed, dried and cooled tobacco 12 with minimal damage to processing. The vapor / water layer 36 provides a drop-covered area where the tobacco 12 falls before the start of the process through the re-humidifier 34. In the re-humidifier 34, the layer of dried tobacco 12 is flushed with steam to increase the moisture content of the tobacco 12 to an appropriate level of about 15% humidity. Using a low-pitch vibrating conveyor, the tobacco 12 is fed through the steam tunnel 40 of the re-humidifier 34. This allows the dried and re-humidified tobacco 12 to pass through the re-humidifier 34 without mechanical impact, which would damage the dehumidified material 12. .

The dryer 38, as indicated, consists of five independent drying zones 22, 24, 26, 28 and 30 through which the endless conveyor belt 14 passes.

The conveyor belt 14 carries the tobacco 12 at about 7.62 cm (3 inches) thick and is 213.3 cm (7 feet) wide. The conveyor 14 is a single conveyor that passes through each of the drying zones, as well as the cooling zone, to minimize damage from processing.

Tobacco 12 enters the dryer 38 from a hopper with about 30% moisture content, as shown in Figure 2. In each drying zone, heated air 50 is introduced into the exhaust ventilation 52 shown in FIG. 3 at the following pressures and temperatures:

Zone Air temperature Ventilation pressure Heating zone 1 93.3 ° C (200 ° F) to 137.8 ° C (280 ° F), preferably 104.4 ° C (220 ° F) 6.35 cm (2.5 inches) water column Heating zone 2 93.3 ° C (200 ° F) to 137.8 ° C (280 ° F), preferably 104.4 ° C (220 ° F) 5.08 cm (2.0 inches) water column Heating zone 3 93.3 ° C (200 ° F) to 137.8 ° C (280 ° F), preferably 104.4 ° C (220 ° F) 3.81 cm (1.5 inches) water column Heating zone 4 93.3 ° C (200 ° F) to 137.8 ° C (280 ° F), preferably 104.4 ° C (220 ° F) 2.54 cm (1.0 inch) water column Heating zone 5 93.3 ° C (200 “h to 137.8 ° C (280 ° F), preferably S4.4 ° C (220 ° F) 1.27 cm (0.5 inch) water column Cooling zone 1 18.3 ° C (65 ° F) to 21.4 ° C (85 ° F), preferably 23.8 ° C (75 ° F) 1.27 cm (0.5 inch) water column

The heated air 50 is then introduced through a plurality of jet tubes 54 and collides with tobacco 12 at a speed of about 304.8 to 914.4 m / min (1000 to 3000 feet per min). The fluid tubes 54 in fluid connection with the pressure ventilation 52 are hollow and about 30.48 cm (12 inches) long. The temperature of the heated air 50 in the exhaust ventilation 52 in zone 1, dryer 22, is about 93.3 ° C (200F) to about 137.8 ° C (280 ° F), preferably about 104.4 ° C (220 ° C). F). As indicated, each area of the dryer 38 is independently controlled and has its own inlet and outlet for heated air, as shown in FIG.

The conveyor belt 14 carries the tobacco product 12 throughout the dryer 38 at a rate of about 39.62 cm / s. The drying zones 2, 3, 4 and 5, represented by the corresponding headings 24, 26, 28 and 30, operate with an air temperature between 93,3 ° C (200 ° F) to about 137,8 ° C (280 ° F) preferably at 115.56 ° C (240 ° F), and enter the air 50 through the pressure ventilation 52, at the settings defined above. The different temperatures applied to each drying zone are used to minimize the hardening and corrosion that can occur when trying to dry a tobacco sheet at high temperature. The total residence time of tobacco 12 in the oven 38 is only about 60 s. The dryer 38 is approximately 24.38 t (80 ft) long and 2.13 m (7 ft) wide. Tobacco 12 at the inlet of the dryer 38 has about 30% moisture content. At the outlet of dryer 38, tobacco 12 is evenly dried to approximately 5% moisture content, roughly 10% of the time it would take to dry tobacco in standard, commercially available oven dryers.

As shown in FIG. 3, the drying zones 22, 24, 26, 28 and 30 have a plurality of jet tubes 54 which are fluidly coupled to the pressure ventilation 52. The jet tubes 54 introduce heated air downstream of the tobacco layer 12 with minimal agitation. of tobacco 12, which causes a uniform drying through the tobacco layer and prevents moisture content variations in the thickness of the layer. Precise drying of the tobacco material is required due to the formation of pyrazines, the removal of irritating volatiles and the improvement of the workability of the leaves. The drying of tobacco material should be carefully controlled due to the drying of heavy veins applied prior to this process, as inappropriate drought cannot cause the veins to harden and cause the tobacco leaf to become curled.

As shown in FIG. 3, the air 50 injected through the jet pipes 54 is recycled back through each drying zone 22, 24, 26, 28 and 30, as well as through the cooling zone 32, through the return channels 58 and 59. to prevent the dried tobacco material 12 from entering the exhaust air from the return lines 58 and 59 on each of the dryers, balancing the blower and blower fan for each zone is required. The heated air 50 is provided to the injection ventilation 52 by the intake air from the plurality of jet tubes 54. The air 50 is introduced against the moving bed of tobacco 12 at a high speed value. The air 50 returns on both sides of the outlet ventilation 58 and 59 shown in FIG. 3 for back-circulation through the independent drying zone. The air is recirculated into the drying or cooling zone, creating a closed system that can be easily balanced by adjusting the air inlet and outlet fan. Tobacco layer 12 requires very little residence time in the dryer 38 in order to properly dry the material to the required level, typically about 60 s.

As a result of the drying process, pyrazines are formed in the tobacco. The amount of pyrazines formed is directly related to the temperature at which the tobacco is dried and also to the total drying time. The formation of pyrazines affects the taste and real attractiveness of the smoking material. As a result, tobacco drying must be rigorously analyzed to ensure that the chemical composition of pyrazines in tobacco remains constant from process to process. Figure 5 shows a graph of pyrazine formation at different drying temperatures. Drying tobacco 12 using the oven 38 at an air temperature of about 120 ° C (248 ° F) causes little or no difference in the total content of pyrazines. The change in the total drying time also affects the formation of pyrazines and needs to be further controlled. With the method of the invention, pyrazine formation remains completely constant until dried at about 120 ° C (248 ° F), although the drying time is reduced by more than a minute to 90 s. Thus, the reduction in the total drying time using a method and apparatus such as those described herein can be achieved, while achieving uniformity in the re-drying of the tobacco to approximately 5% moisture content.

After passing through the oven 38, the tobacco has approximately 5% moisture content. Because tobacco has such a low moisture content, it is susceptible to damage and breakage, so processing must be minimal. Before using tobacco 12 in the manufacture of cigarettes, it must be re-moistened, since the required moisture content of tobacco in the finished cigarette product is about 15%. For this purpose, the tobacco 12 must be passed through a cooler 32 that uses the same jet tubes 54 as shown in FIG. The air 52 used in the cooler 32 has an ambient temperature of approximately 23.8 ° C (75 ° F), cooling the tobacco in the tobacco layer to about 26.6 ° C (80 ° F). The total residence time of tobacco 12 in cooler 32 is about 15 s and requires only about 6.1 m (20 feet) of process length to reduce the temperature of the tobacco to the appropriate.

The tobacco enters the re-humidification phase to raise its moisture content to the appropriate levels, from 5 to about 15% moisture content. In order to allow the passage of tobacco from the conveyor 14 into the steam tunnel 40 of the re-humidifier 34, a transitional vapor layer 36 is provided. The transfer station 36 is a steam / water layer that takes the tobacco from the conveyor to the steam tunnel 40. The difference in height between the conveyors 12 and the transfer station is about 106.7 cm (42 inches). A cover of steam or water from an independent pressure source is provided at the beginning of the re-humidifier 34 to cover the fall of the tobacco material 12 and to provide an initial high-density humidity zone while ensuring that product degradation is minimized . This drip / vapor zone 34 is located at the inlet for charging the steam tunnel 40. The steam or water source, as indicated, is independently controlled and can be controlled independently of the steam tunnel 40. The vibration conveyor system of the re-humidifier 34 takes over at this point and moves the tobacco material 12 upwards at a slight upward slope through the steam tunnel 40. The steam tunnel 40 shown in FIG. 4 consists of a base 60, side walls 64 66 and a plurality of nozzles 62 formed in base 60 walls 64, 66 which are in direct connection with the steam source. The re-humidifier 34 has an inlet angle of about 2.5 ° and moves the tobacco layer, which is still about 7.62 cm (3 inches) thick at the base 60, using vibration transport. The plurality of nozzles used in the steam tunnel 40 provides a fine mist of moisture to increase the moisture level of the tobacco layer uniformly without large deviations in each sample area. The steam tunnel 40 is about 6.1 m (20 feet) long , 2.13 m (7 ft) wide, coinciding with the width of the dryer 38 and the cooler 32. Tobacco 12 has a total residence time of the re-humidifier of only about 15 s. The moisture content of tobacco 12 at the outlet of the re-humidifier 34 is 15% throughout the volume.

The apparatus 10, the dryer, the cooler and the re-humidifier of the preferred embodiment of the invention have a total length of about 36.6 m (120 ft) and is 2.13 m (7 ft) wide. The operating capacity of the method and apparatus of the invention is approximately 6350.4 kg / h at the outlet of the re-humidifier. The total residence time of the tobacco in the oven, cooler and re-humidifier is about 90 s. This is a noticeable improvement over state-of-the-art dryers and re-moisturizers that require a total residence time of about 20 min, have a length of more than 60.96 m (200 ft), and have an output of about 4356 kg / ft at the outlet of the re-humidifier. h.

This description is exemplary and does not constitute a restriction on modifications which are apparent to those skilled in the art and can be made without departing from the spirit of the invention and the scope of the claims.

Claims (22)

Claims 1. A method of drying and cooling tobacco, comprising loading tobacco onto a conveyor belt with a predetermined thickness of the tobacco, transferring the tobacco onto that conveyor belt through a heated air dryer, transferring the tobacco through a cooler and subsequently moistening the tobacco, characterizing the tobacco in that the transfer of the tobacco into the oven further includes supplying air heated to a first pre-selected temperature in a first heating zone for drying and creating a fluidized bed, recirculating the air into the oven. ditch the heating zone, supply air heated to a second pre-selected temperature, in a plurality of heating zones, following the first heating zone, recirculate the air in the plurality of descending heating zones, such as the air temperature in each zone in the order of 93 , 3 ° C (200'F) - 137,8 ° C (280 ° F), raising the temperature of the tobacco to the same limits and reducing its moisture content to about 5%, transporting the tobacco by conveyor belt to the cooler operating in a fluidized bed with atmospheric air , transferring the tobacco into a humidifying tunnel, operating with a vibrating conveyor, and humidifying the tobacco in a humidifying tunnel. Method according to claim 1, characterized in that the predetermined thickness of the tobacco layer is approximately 7.62 cm (3 inches). Method according to claim 1, characterized in that the tobacco is carried through the oven and the cooler at a rate of approximately 39.6 cm / s (1.3 ft / s). A method according to claim 1, characterized in that the first preselected temperature is approximately 104.4 ° C (220 ° F). The method according to claim 1, characterized in that the second preselected temperature is approximately 115.56 ° C (240 ° F). Method according to claim 1, characterized in that the air in the first heating zone and the plurality of descending heating zones is contained in a closed system. A method according to claim 1, characterized in that the cooling of the tobacco further includes: directing ambient air to the tobacco, recirculating that air into the cooler and reducing the tobacco temperature to approximately 26.6 ° C (80 ° F). A method according to claim 1, characterized in that the re-humidification of the tobacco further includes: transporting the tobacco through said steam tunnel using a vibrating conveyor, injecting steam into the steam tunnel from a plurality of sources, and increasing the moisture content of said tobacco. tobacco up to about 15%. Method according to claim 1, characterized in that the pressure in the first heating zone is about 6.35 cm (2.5 inches) of water column. 10. The method of claim 1, wherein the overpressure in the second heating zone is about 5.08 cm (2.0 inches) of water. 11. The method of claim 1, wherein 5 because the pressure in the third heating zone is about 3.81 cm (1.5 inches) of water. A method according to claim 1, characterized in that the pressure in the fourth 10 heating zone is about 2.54 cm (1 inch) water column. Method according to claim 1, characterized in that the pressure in the fifth heating zone is about 1.27 cm (0.5 inches) aqueous 15 pillar. A method according to claim 7, characterized in that the overpressure in the cooling zone is about 1.27 cm (0.5 inches) of water column. A tobacco drying and cooling apparatus for carrying out the method according to claim 1, comprising a drying unit (38) comprising a plurality of independently controlled drying zones, characterized in that a cooling unit (38) is provided to the unit (38). 32) with one cooling zone, a belt conveyor (14) passing through the drying and cooling unit, one located at the end of the belt conveyor (14), a transitional zone with a steam layer (36), and a humidifier (34) containing steam tunnel and vibration conveyor connecting the transition zone with steam and the extended outlet of the humidifier (34), the drying unit (38) comprising a first (22), second (24), third (26), fourth (28) and fifth (30) air-ventilated heating zones from 93.3 ° C (200 ° F) to 137.8 ° C (280F). Apparatus according to claim 15, characterized in that the vibrating conveyor is constructed as a base (6), located at a 2.5 ° upward slope. Apparatus according to claim 15, characterized in that the dryer (38) is arranged to operate with a fluidized bed of tobacco material. Apparatus according to claim 15, characterized in that each of said heating zones of the dryer (38) includes means (58,59) for recirculating the heated air. Apparatus according to claim 15, characterized in that the cooler (32) comprises a cooling zone, which includes means for subjecting the tobacco (12) to ambient air from above. Apparatus according to claim 15, characterized in that the belt conveyor (14) operates at a rate of approximately 39.6 cm / s (1.5 ft / s). Apparatus according to claim 15, characterized in that the humidifier (34) further comprises a floor conveyor base (60), a first and a second side wall (64,66) and a plurality of nozzles (62) in fluid communication with a steam source, the plurality of nozzles being formed on the floor conveyor surface and on the first and second side walls. 22. The apparatus of claim 15, wherein 5, wherein the vibrating conveyor moves the tobacco at a rate of approximately 39.6 cm / s (1.5 ft / s).