The fresh air (1) is absorbed in the lower area of the drying plant, heated up by a gas line burner (2) and together with preheated supply air delivered from the cooling zone area (3) to the lower drying section, the dry product area (4). The hot air temperature can be adjusted completely independent of the upper temperature zone. The higher tempered exhaust air (5) from this zone is collected and led into the upper area of the drying plant by means of an intermediate fan (6). By mixing with preheated supply air (7), the hot air of the upper drying zone is generated. This drying air is firstly led through the upper wet product area (8), before it is discharged to atmosphere again as exhaust air by an exhaust air fan (9).
from 0.922 kWh/kgH2o thermal energy demand
Due to this energy-efficient air duct system, a thermal energy demand ex 0.922 kWh/kgH2O is obtained. This value is ca. 15 % below the usual energy consumption of comparable drying plants without this specific heat recovery. This results in an energy consumption of 216.7 kWth when drying one tonne of wet maize with a moisture reduction from 35 % to 15 %, this equates to ca. 20.9 m³ of natural gas (calorific value 10.35 kWh/m³).
Innovative STELA Biturbo technology with oil heating
Besides gas heating, air heating by air heater (1) with oil fan burner (2) can be realized as well. In order to guarantee also in this case a compact and mainly energy-efficient functionality, STELA Laxhuber turned their attention especially to the positions of both direct air heaters when designing and constructing the air duct system. Thus they ensure that the thermal energy demand is from 0.922 kWh/kgH2o as well. This results in an oil consumption of 21.7 litres for the drying of one tonne of wet maize with a moisture reduction of 35 % to 15 %.
Further advantages of the Biturbo technology:
- reduced air volume
- improved product quality through alternating ventilation
- less dust formation due to the exhaust air filtration in the wet product area
- lower electric consumption.
For the constructive layout of your drying plant, there are numerous variations, which can be individually arranged. You will receive an optimum design for your application with the adequate components in compliance with your wishes. Generally applies for all variants: The pourable drying product is conveyed into the storing tank (1), flows due to gravity through the drying (2) and cooling elements (3) and is then discharged at intervals by the discharge unit (4) into the discharge hopper (5). There are the most various alternatives for the necessary air heating, according to which the types of drying plants are selected. These types are further distinguished according to exhaust air treatment/dust separation and the type of air duct technology for energy saving.
Construction with passive heat recovery from the cooling zone and dust separation by pneumatic flap.
Air heating/air duct system
The exhaust air of the cooling elements is mixed with the fresh air heated by the burner (6) and the air heater (7) – optionally direct and indirect firing is possible. Thus the complete heat stored in the dried product is fed back to the drying process. The large-dimensioned hot (8) and exhaust air caps (9) guarantee an optimum air and heat distribution in the drier column. The hot air sweeps through the product bed, absorbs moisture and is then sucked off by the exhaust air fan (10) from the exhaust air cap.
Exhaust air treatment
By means of a pneumatically operated exhaust air flap (dust separation flap - 11), installed at the exhaust air fan (10) at pressure side, the air flow is interrupted during the discharge cycle. Blocking the airflow avoids that the dust in the product is emitted during the discharge process.
Construction with centro separator and recirculating air system for active heat recovery.
Air heating/air duct system
In this example, the air is heated by means of a gas line burner. Furthermore, not only the exhaust air from the cooling zone, but by means of a separate recirculation fan (1) also the exhaust air (and thus the energy in it) from the lower drying elements is recycled. The recirculation airflow is blocked during product discharge by using a pneumatic recirculation air flap (2) and so the dust in the product is restrained.
Essential for the percentage of the total air volume which can be recycled as so-called recirculation air are among other things the initial moisture of the product, which can be expected on average, as well as the parameters of the ambient air. So the driers are calculated and designed depending on the location – e. g. Central Europe, Southern Europe or the tropics. A drying plant in Central Germany with the main task of drying maize with an average initial moisture of 35 % requires another air division than e. g. a drier in Southern Hungary with average initial moistures of 20 %.
Exhaust air treatment
The dust loaded exhaust air is sucked off by a radial fan (3) and cleaned in the centro separator (4) according to the German Clean Air Guidelines before it is discharged to atmosphere. The separated dust is conveyed e. g. via pipes to a bagging unit or is transferred without pressure to a further conveying unit by means of a dust lock
Overview of Stela drying plants
- Use of the highest quality materials
- Dryer from special aluminium alloy
- High life span
- No upper limit to capacity
- Optimal energy saving through Biturbo technology, circulating air systems and heat recovery
- Sophisticated air guidance, highest possible air saturation
- Highly efficient
- Flexible modular construction
- Dust separation with state-of-theart technology
- High performance industry fans from own production
- Continual operation for optimal utilization and exploitation
- Uniform product moisture by modern discharge technology
- Suitable for indoor and outdoor installation
- Plants with one or several columns; divided operation modes as desired
- high energy saving due to EQtronic and a special moisture control
- guaranteed low dust emission values in accordance with the German Pollution Control Act (BImSchG/TA-Luft)
- TÜV-tested indirect air heater with efficiency factor > 90%
- noise insulation equipment for a minimum of sound emissions