Batch vs Continual Mixed Flow Grain Drying


Continuous technological innovations have paved the way for advances in agri-processing equipment, allowing farmers a wider variety of options when choosing grain drying equipment. The improved technology available today places farmers firmly in control of their drying costs and quality control. The affordability of the equipment as well as the cost-saving parameter it provides makes it extremely financially viable.

In this system, a volume of grain is loaded into a Batch Dryer and dried to the required moisture content
level. The volume loaded is determined by the holding capacity of the dryer. Once the drying process is
finished, the dried grain is unloaded from the dryer, and a new batch of wet grain is loaded in; thus,
the drying cycle continues. Batch drying, therefore, requires loading and unloading time for each batch of grain. Batch grain dryers have the disadvantage of over-drying the grain close to the wall of the incoming hot air. The grain losses its moisture first to the hot air, whilst the grain lying further away in the dryer takes longer to dry. This results in large variances in moisture content across a batch and can greatly impact the grain quality. The difference in grain moisture level between the layer nearest to the hot air and the outer layer varies with the dryer’s column thickness, the temperature of hot air, and the airflow rate. Batch dryers in the market can either have a stirring or a mixing option; because these are mechanical in nature, they can result in damaged grains.

Column grain dryers that operate in a continual process are known as Continuous Mixed Flow grain dryers. To start the drying process, the wet grain is fed into the dryer and passed through the heating elements. The grain is mixed as it passes through the heating elements. Drying of the grain is ensured by two factors that are; airflow in both counter and concurrent directions, and the non-mechanical mixing effect of the grain. The grain is tested during the drying process to check moisture content and if further drying is required, the grain is recycled through the machine. Once the grain has reached the desired moisture level it is discharged at one end and wet grain is immediately loaded in at the same time at the start point, ensuring a continual process.

The continuous mixed flow drying system presents numerous advantages which include;

  • The incorporation of a cooling phase in the drying column.
  • The dryers are usually self-cleaning and are energy efficient, using about 40% less energy than a conventional batch dryer without heat recovery.
  • The high degree of automation of these machines means a huge cost saving in terms of labour.
  • It offers lower operating costs and uniform grain moisture content ensuring better quality outcomes
    compared to batch drying systems.

As compared to batch dryers were all-grain kernels are exposed to the same air temperature; continuous
mixed-flow grain dryers often have multiple heat zones and can use higher air temperature without causing crop damage. Another advantage of the continuous mixed-flow grain dryers when compared to a batch
dryer with a screen column is the ability to use the dryer for a wide variety of different grains; from small
rapeseed to wheat, maize or soybeans.

For more information on grain, dryers contact Corpcord Investments at or +263 775 463 205

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