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Drying seeds with dehydrated air

Dehydrated air by adsorption or special Hybrid dryers.

Description rotor

The centre of a dehumidifier is the rotor or adsorption wheel. This part consist out of a chemical bound silica gel that can adsorb moisture out of the air that pass the rotor but can also release moisture during the regeneration process.

After the regeneration process the rotor is ready to adsorb moisture again.

The structure of the rotor looks like honeycomb pattern with a lot of small air channels. All these air channels make a big adsorption surface which takes care of the dehydration of the air that passages the rotor; the silica gel absorbs water from the air.

Regeneration of the rotor

The silica gel in the rotor cannot absorb water unlimited. Nevertheless the adsorption process is a continuing process. To make the adsorption process a continuing process the construction of the rotor is designed to absorb water at 75 or 50% of the total surface of the wheel. 25 or 50% (depending the T° of the regeneration air) of the rotor is used for regeneration (drying the rotor).

Rotor with 75-25 configuration; regeneration by hot air (150°C) from gasburner ad 25% of the rotor surface.
Rotor with 50-50 configuration; regeneration bij warm air (60°C) from hot water battery or condensor.

By rotating, each part of the rotor will absorb water and will later being dried by regeneration. The regeneration section is isolated from the adsorption section. By blowing hot air through the regeneration section, the adsorbed water will be removed from the rotor. The moist regeneration air will be evacuated trough air-channels to outdoors.

Basic principle for Adsorption Dryers

P: Moist process air into the air dryer
1: Process air will be filtered
2: Process air will be dried by the rotor
3:Dry and (warm) process comes out of the airdryer and can be used for drying MAP

R: Regeneration airflow to dry the rotor
4: Regeneration air will be filtered
5: Regeneration air will be heated (60° or 120-150°C)
6: Regeneration air will dry the rotor
7: Moist regeneration air will be evacuated tooutdoor.
8: Heat exchange unit

Option I) 8: Heat exchange unit brings proces air T° down to the ambiant level + 3°C. Free coming energy will be used to warm up regeneration air; Energy saving.

Option II) 9: Cold water battery (chiller) with modulated capacity can cool down the process air to any desired T°C. Hybrid system

Option III)  Combination  8+9: Energy saving and reaching any desired T°C for out coming process air. Hybrid system with heat-exchange

Economically and modulating drying of air; The hybride principle

Hybrid heat pump with cold water

The hybrid air dryer is specially developed to create very dry air with an constant (low) temperature of the process air. Process air is first being cooled, so water in the process air will Condensate on the evaporator. After this, the process air at 100% HR will be dried to a low level by the Adsorption rotor. Because of high HR, the capacity of the adsorption rotor is at its maximum. The capacity of the evaporator is modulating; The process air will be cooled to a level by which the out coming process air is at the desired T°.

 

Regeneration air will be heated by the condenser (heat-pump) and an additional radiator with hot water. Less external heating is needed and all energy will be used; energy saving!

The rotor will be dried by this hot air. A heat-exchange unit in the outlet of the regeneration air can pre-heat the extracted (cold) air for regeneration; extra energy saving!

Hybrid heat exchanger

Hybrid installation with heat-pump en heat-exchange units. Automatically extraction process-air direct from outside or by heat-exchange unit for maximum energy saving. Modulating heat-pump for 100% result in summer and winter.

Big advantage of adsorption air dryers is that the maintenance costs and frequency for services is low.

Different air dryers can be used in several occasions where dry air is needed. We have mentioned some possibilities above. The final implementation and capacity depends which parameters are required. Regeneration process can be done by gas burner, hot water radiator or condenser (with extra radiator). Temperature can be controlled by installing a modulated air-air cross-exchanger, a cold water battery which must be connected to a cold water chiller or by a heat-pump installation. All controlled by the ABC processor.

Energy can be saved by installing a (modulating) air-air cross heat exchanger in the process air stream. The optimal and most economical air dryer is the ACR dryer from Agratechniek; When very dry process air (down to 1.5 gr/kg air) is needed at a low T° (down to 15-20°). Modulating capacity and energy saving!