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Drying grain with aeration and heat: discover how it works




Drying is an important process for the conservation and market of many crops, first of all cereals and legumes. One of the most effective ways of removing moisture from cereals is by drying grain with aeration and heat: but how exactly does this process work? And with what tools can it be performed effectively? In this article, Mecmar offers you some useful information on this topic.

How the cereal drying treatment works

At the time of harvest, cereals and legumes have a certain moisture content depending on the product (in general the rate typically varies between 18 and 25%). This excess of water, present in the grains, must be reduced by up to 13% to avoid compromising the quality of the cereal and, during the storage period, to defend the kernels from attacks by microorganisms and degrading consequences in their chemical components.

For some products, such as corn, the drying process is not natural but artificial: in fact, the solar radiation in the ripening and harvesting period is not sufficient to evaporate the water, as generally happens for summer cereals. By pushing forced air around the grains and, even better, by heating the blown air, it favours the surface evaporation of the grains; the internal air tends to rise towards the surface in order to be then removed by the subsequent passage air.

For an effective and efficient drying, it is necessary to find a balance between speed and temperature, which allows to carry out the drying process in the shortest possible time and with the minimum consumption of energy and form of heating, without using the grain depending on the end use (sowing, livestock or food industry).

In the consequent drying process, it is essential to:

  • Choose the right drying temperature, taking into account on one hand the maximum temperature that the product can withstand without altering its nutrient or germinative constituents and on the other hand the temperature that guarantees the maximum speed of water diffusion inside the product;
  • Determine the optimal flow of air to blow, which allows to establish the balance between the rate of diffusion of the water inside the product and its evaporation rate, so that the air can leave the mass to dry, always completely saturated with water.

The drying process, originally, was an extremely natural process, carried on thanks to the heat of the sun. The procedure was very simple and it consisted in placing the individual grains on a sheet, in a thin thickness, in the way that the sun's rays could hit and slowly dry them, thanks to the evaporation of the water. This is a process that takes a long time (from 3 weeks to a month) and that does not ensure to have full security on the right drying of each product. In addition, during the drying period, cereals easily risk being stolen or eaten by birds and rodents.

The treatment that consist of drying grain with aeration and heat is different: this is a more innovative and functional technology, effectively carried out by specific machinery. These machines are the grain dryers, specifically designed to remove the excess moisture content from the beans, drying them without damages.

The grain dryers

The grain dryers are designed precisely for drying grain with aeration and heat: the combination of these two elements, adapted from time to time for the product to treat, allows to obtain perfectly dried grains, ready for storage, for sale or even for subsequent treatments.

Using a grain dryer, it can be removed up to 5% of humidity per hour of hot air blown in the case of corn, while for rice it’s possible to remove up to 1.3-1.5% of humidity. The dryers allow to reduce drying times and, even with a machine of compact dimensions, it is possible to dry hundreds of tons/grams of cereals.

Mecmar dryers are able to guarantee an optimization of consumption and excellent homogeneity in the dried product in the shortest possible times thanks to two key points: the optimal balance between the process parameters and the continuous recycling and mixing of the product inside the dryer.

The operation of a dryer finds its effectiveness in its ability to eliminate excess humidity through hot air: the partial separation of water from the single grain always takes place by evaporation, but in a much faster and safer way. Depending on the type of cereal and end use, the method and process parameters vary, although the Mecmar machine is always the same.

Do you want to know more about grain dryers? Then you may be interested in the following articles:

For every specific needs there are different models and types of dryers: the main subdivision is made between mobile grain dryers and tower dryers. The first are solutions that operate in a discontinuous cycle and whose particularity consists in being transportable and easily repositioned according to the needs, since they are equipped with wheels that make them very easy to move. We move from smaller and more compact models (such as Mecmar NANO 5/40 or STR 11/100 models) suitable for farmers or small agricultural cooperatives, to more structured and larger capacity models (such as the SSI 25/203 model or the largest of the Mecmar range, the dryer F 75/570).

Tower dryers, on the other hand, are the ideal solution for large farms and storage centers, which need a higher hourly production, which can be answered in these systems thanks to their continuous drying cycle. In this case, Mecmar offers tower dryers that adapt to different drying needs, such as the RT 225/10 model or the larger RG 600/18 model.


Drying grain with aeration and heat, thanks to dryers, is an advantageous choice that allows you to avoid product losses due to the humidity present in the cereals following the harvest. The process carried out by the dryers is fast and safe: the grains are dried without compromising the quality of the cereal and the excess humidity is removed to allow long-term storage.

Mecmar has a long experience in the field of design and construction of grain dryers, both mobile and tower dryers. If you want more information about our solutions and find the one that best suits your requests, do not hesitate to contact us: the Mecmar team is ready to answer to all of your questions.£$Download the calculator

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