Technological and Technical Development of Tobacco Drying

'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).