Rotary Dryer Design 101: Defining Your Atmosphere

This article was co-authored by:

Shane Le Capitaine
Thermal Processing Expert

Carrie Carlson
Technical Writer

In addition to the many material characteristics that must be considered during the sizing and design stages of engineering a custom rotary dryer, there are also a few operating environment factors to consider as well.

Atmosphere Considerations: Humidity

Humid air is already moisture-laden, meaning that some, or much of its moisture holding capacity, is already occupied. In contrast, dry air has little moisture in it, and therefore has the capacity to absorb more.

Because water has a very high specific heat, meaning it requires much more energy to cause a temperature change, air that is humid will be much more resistant to temperature change. As a result, a significantly greater amount of BTUs will be required to dry the material in a humid environment.

Addressing Humidity Through ROTARY Dryer Design

Dryers intended for use in humid climates will require a more substantial burner to accommodate the high amount of energy required

Atmosphere Considerations: Ambient Temperature

The ambient air temperature in which the dryer will operate is also an important factor to look at, especially in the event that the dryer will not be in a climate-controlled environment.

A dryer that will be operating in a generally cold environment will require much more energy to heat than if it were operating in a warmer environment and vice versa.

Addressing Ambient Temperature Through ROTARY Dryer Design

Dryers operating in hot temperatures can be designed for much less demanding energy requirements than those working in cold temperatures. This affects burner, fan, and motor selection.

Climates that experience drastic changes in temperature and humidity, such as in the Midwest United States, must find a balance between the most common operating conditions and the desired efficiency.

Atmosphere Considerations: Elevation

The elevation at which the dryer will operate also plays a role in rotary dryer design. At higher elevations, the air contains less oxygen, so it is much less dense. As a result, the volume of air effective at sea level is typically not going to be as efficient at a higher elevation.

Addressing Elevation Through ROTARY Dryer Design

Due to the lower density of the air, a higher volume of air flow will be required to reach the desired result at higher elevations.This will also require a larger fan and potentially, a more powerful burner and motor.


FEECO is the leading supplier of custom rotary dryers. All FEECO dryers are engineered around the specific requirements of the material and process goals to produce a system that operates efficiently and reliably. For more information on rotary dryer design, contact us today!

About the Authors . . .

Shane Le Capitaine is a Process Sales Engineer and thermal processing and fertilizer production expert.

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Carrie Carlson is a technical writer and visual designer.

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