Technological and Technical Development of Tobacco Drying

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Table 2. Comparison of the component features of differently cured tobacco Curing method Carbohydrate Reducing sugar Total nitrogen Nicotine % % % % Conventional 14,38 9,45 2,56 2,18 Advanced 17,62 12,81 2,23 1,87 It is now clear that measurement with the advanced (new) technology resulted in more favorable levels of some important chemical components, that is, it was produced a better quality at the end of the curing of Virginia type (H-11) tobacco. TECHNICAL DEVELOPMENTS It is well known, that under curing of flue-cured tobacco, the task is not only to remove the water from the leaf but also to help the enzyme changing in the tobacco. Most of the curing barns using in Hungary have many drawbacks. 'The circulation of the drying air works in opposition to the natural position of the hanged up tobacco leaf. The air bowled upwards from below moves the leaves, the laminas are compressed, so the distribution of air circulation is uneven and the air-resistance is increased because of the deviated leaves. In this case a higher capacity fan is required to maintain the necessary ventilation. The intensive air-circulation of the bigger fan results a higher pressure in the curing chamber, so there is a continuous blowing through the gaps of the barn. It means a considerable heat-loss and vapor decreasing. The deficit of the temperature sets back the economic result and the lower relative humidity causes a worse quality of the end product. When the air-circulation happens upwards from below, at first the laminas are touched intensively by the air, so they will be dried out earlier than the veins and midribs. Due to this effect, it needs much time and energy to reach the end of curing, while the valuable parts are over dried. 'The heat insulation of the curing barns is not solved perfectly, especially at the old type "SIROKKÓ" equipments. In the period of curing, big amount of radiated heat can escape - mainly in the night -, which means plus cost maintaining the temperature balance . Figure 5. Rack type tobacco drying equipment
'There is another disadvantage, that the existing curing barns can only be used in a short period of the year, so the utilization rate is bad. Generally we can say, that the surplus expenditures is not realized in the quality of the cured tobacco and income. Our purpose has been to develop a new method and equipment, which eliminates the above detailed disadvantages and results some forwarding solutions. It has been verified experimentally, that if the tobacco leaves are hanged up in racks as usually and the curing air is circled evenly from above to downwards, then the laminas of the leaves are bowled as a flag in the direction of the circulation. It is such a surplus effect, which assures a lower resistance and uniform air-ventilation in the curing chamber. In this case the energy demand of the ventilation is less, than the same volume curing air circulated upwards from below. It can be guaranteed a constant intensity air movement in the whole cross-section of the barn by the evaporating air, forced in the direction of the gravitation. It is a condition of the uniform and homogeneous drying(Figure 5.). The heated air is circulated from above to downwards, touches the upper part of the high water content midrib at first, so the too early drying out of the lamina can be avoid. It was a surplus recognition, because this solution can assure favorable heat-effect for the whole leaves. On the other hand, the protected leaf lamina has a smaller heat-load and it has a chance to maintain an optimum respiration process, during the yellowing and color fixing. The uniform air-distribution and the homogeneous curing render a precise temperature and relative humidity monitoring and control in the barn. It is also a condition of reaching the best color and chemical components for the end of the schedule (Kerekes – Lengyel, 1998). It can also be reached the same similarity, when the tobacco is humidified, after finishing the process. We can avoid the uneven moistening, which causes spots on the surface of the leaf. Another new recognition, that an overshadowing screen can solve the recovering of the radiated heat-loss. It means, that the heat - which radiated out from the wall of the barn - is gathered by a special screen, so the air-space between the chamber and the screen is used as recuperator, which pre - heats the exterior air, drawing in for curing. Moreover, we recognized, that if we established a light - permeable cover over the heat - screen, we would produce such a heat-trap, which could utilize the energy of the sun. This simple sun - collector would pre-heat the entered curing air. Finally, it was a new idea, that when the curing barn was out of the basic function, the transparent cover could be moved back on rails, so the system could work as a greenhouse, running by the thermo generator of the barn. This multi-purpose utilization guaranteed a more economical work. In our region most of the curing barn can reconstruct for drying of fruits or vegetables. In the Figure 6. you can study the setting up of the multi-purpose curing barn. In Hungary many smaller tobacco curing barn were developed in the past ten years, according to the requirements of the tobacco growers and the processing enterprises. When starting production of the Virginia type tobacco, the cooperatives used mainly the big capacity "SIROKKÓ"-type barns. Most of these equipments were working continuously after the privatization, but they consumed too much energy and they were not able to produce a high quality dried tobacco. 'They must be renewed and reconstructed in the near future. We have made an extended experimental and practical examination, regarding to the stated new development (Kerekes – Lengyel – Sikolya, 1997).
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Page 5: Air demand, [kg/kg wate Heat demand
Page 9: The Table 3. represents the results

Technological and Technical Development of Tobacco Drying

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