ANTTI Vacboost M13, Installation And Operating Instructions Manual

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Antti-Teollisuus Oy 58 408111 03-2019
Vacboost M13
An example of the drying air's ability to absorb steam with the same amount of heat, mixed with different amounts
of air:
For warming 10,000 m³ of air from 0 °C to 50 °C is required the same amount of heat than for warming 7,100 m³ of
air from 0 °C to 70 °C. Blowing these amounts of air through the grain layers in the dryer, will drop the temperature
by the middle of the drying time to about 20 and 27 degrees respectively. Then 10,000 m³ of air at +20 °C can at
maximum contain 170 kg of water and 7,100 m³ of air at +27 °C can at maximum contain 188 kg of water. When
the air at 0 °C can contain 5 g of water/m³, then with 10,000 m³ of air at 50 °C will go in 50 kg and come out 136
kg (= 86 kg net), and with 7,100 m³ of air at 70 °C will go in 35 kg and come out 150 kg (= 115 kg net).
In practice, the higher the temperature inside the corn during drying, the quicker the water will evaporate causing
a pressure difference. This improves the drying efficiency even more than theoretical calculations suggest.
If you are aiming at good economy, you should in certain situations reduce the air amount even if there is no true
need to raise the temperature. The aim is to make the air flow through the grain layers sufficiently slowly. If the air
is flowing too fast, it may not be able to evaporate the amount of water entirely that it otherwise would be able to
absorb. If the air leaves the heater too dry (i.e. too hot), useful heat energy will also be wasted. If you reduce the
amount of air, you may need to reduce the oil flow as well (the 2-stage automation does this automatically). This
is a concrete way of saving energy.
Equilibrium moisture content
The dryer the grain gets, the slower the water evaporates from the grains. As a result, the relative humidity of the
outlet air decreases as the drying proceeds.
How to reduce the amount of air
The flow of suction air into the heater is throttled by means of a manual air shutter.
If you restrict the flow of suction air into the heater too much, the temperature of the drying air will rise too high,
and the upper limit thermostat will stop the burner from time to time Do not let this happen, as it would drastically
reduce the efficiency of the drying process, and strain the dryer heater clearly more than if the production of heat
was constant. For remedy, increase the air flow or reduce the oil flow.