Kilns for curing Virginia tobacco
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Description of tobacco kilns
The kilns are built of metal constructions, chamber type.
They consist of two chambers:
- drying and
- energy
The surfaces surrounding the drying chamber possess an insulation layer with 5 cm thickness. Heat transfer coefficient of the insulation layer is λ ≤ 0.034 W/mK. Panels of the drying facility are covered with painted steel sheets.
Amount of air lost in joints between the surfaces surrounding the chamber, rotating and movable parts is insignificant.
The door of the kiln is closed through an eccentric system. Closing of the door is simple, reliable and effortless.
Energy sources
Energy sources for heating of the drying air:
- conventional energy sources
- alternative energy sources
Conventional energy sources:
- Fuel oil
- Natural gas, LPG etc.
- Coal, wood, pellets, brickets, bio-mass etc.
Alternative energy sources:
- Energy of waste air coming out of the drying process, without mixing with fresh air entering the kiln-heat through heat exchanger.
- Solar energy, solar collectors
- Environmental energy – heat pumps
The boiler room is built outside the kiln, hosting hot water boilers for one or more kilns. The capacity of boilers is determined per number of kilns, based on the demands of simultaneous operating of kilns. The boilers are implemented for conventional energy sources operating at temperatures up to 85°С.
If natural gas is used, than a facade gas boiler is installed in the energy chamber, for heating of working fluid - ethylenglycol.
Energy consumption depends on percentage of alternative energy sources. With use of alternative energy, consumption is decreased by 68% to 90%.
System description
The recirculation of ethylene eglycol is facilitated by the circulation pump, with continuous dosing of energy for heating drying air. Ecological ethylene glycol is used, which is approved for food industry.
Drying of the product is conducted through hot-water heat exchanger ethylene glycol / drying air.
The recirculation and circulation of drying air is conducted by fan.
Maintenance of the parameters of drying is conducted electronically, or with microprocessor, with minimal deviations from set values.
Drying parameters, temperature, humidity and airflow are maintained at programmed-set values, depending on tobacco curing technology applied.
Programming of parameters, when required, may be divided in temperature phases of curing process, or automatically (including all temperature phases).
Tobacco cooling is conducted through an additional cooling medium - ethylenglycol.
Tobacco is humidified with water vapour.
Tobacco cooling and humidification are conducted simultaneously.
Types of kilns
Types of kilns per hot water energy source:
1 - conventional energy source + energy recovery
2 - conventional energy source + energy recovery + solar energy (collectors)
3 - conventional energy source + energy recovery + solar energy + environmental energy (heat pumps)
The kiln capacity is determined by the number of racks.
Delivered with the kiln are the racks on which tobacco is hung, along with tables for reception of racks.
Marking of tobacco curing kilns:
A SD xxx/a-y :
A SD - tobacco curing kiln,
xxx number of racks - capacity,
a - number of channels,
y - numbers 1, 2, 3 determine the type of tobacco curing kiln, per hot-water energy sources.
Example: A SD 60/2-1, two-channel tobacco curing kiln with 60 racks, with energy recovery.
The tobacco curing kilns are produced in capacities of 42, 48, 54, 60, 72, 78 and 84 racks.
All types of tobacco curing kilns feature a system of humidifying with water vapour.
Technical characteristics of tobacco curing kilns:
| type | Number of racks |
Number of channels |
Dimensions | Installed power | Curedtobaccocapacity (kg) | |||
| width | height | length | heat | motor | ||||
| mm | mm | mm | kW | kW | ||||
| A SD 42/2-1 | 42 | 2 | 3260 | 3050 | 5876 | 28 | 2.2 | 357 to 483 |
| A SD 48/2-1 | 48 | 2 | 3260 | 3050 | 6276 | 28 | 2.2 | 408 to 552 |
| A SD 54/2-1 | 54 | 2 | 3260 | 3050 | 6676 | 42 | 2.2 | 459 to 621 |
| A SD 60/2-1 | 60 | 2 | 3260 | 3050 | 7076 | 44 | 3 | 510 to 690 |
| A SD 72/2-1 | 72 | 2 | 3260 | 3050 | 7876 | 48 | 3 | 612 to 828 |
| A SD 78/2-1 | 78 | 2 | 3260 | 3050 | 8276 | 56 | 4 | 663 to 897 |
| A SD 84/2-1 | 84 | 2 | 3260 | 3050 | 8676 | 56 | 4 | 714 to 966 |
Tobacco curing regimes
When yellowing tobacco, at the beginning of the process, relative humidity of drying air is achieved in less than two hours.There is no dissipation of drying air.
Temperature, humidity and airflow are maintained at a programed – set value, depending on tobacco curing technology, that is on the regime of curing of tobacco, with small deviations. Programming of the parameters of curing, regime of drying and drying air flow is divided in temperature phases. Parameters are maintained electronically, with minimal deviations from the set values.
Upon request of the customer, kilns are equipped with a microprocessor system for programming of drying parameters, drying regime and airflow. With microprocessor guidance of the process, the control or potential correction of the regime is done only at the end of tobacco leaf yellowing and root drying.
It is preferable to pick and cure technologically ripe tobacco, because it has the biggest yield, and, accordingly, it gives the best financial results. Picking of unripe and green tobacco is not recommended. Beside lower yield, unripe, green tobacco requires, also, longer tobacco curing time, which increases tobacco curing expenses.
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