The bottom line
In a direct comparison between parameters, Figure 7 shows that an increase in air velocity/volume will provide a significant decrease in drying time and have a dramatic effect on dryer operations that goes
straight to the bottom line. For existing drying solutions, an on-site audit
by trained technicians will usually find these deficiencies and provide
commonsense solutions leading to improved operations.
For example, consider a process that operates with a target product
Figure 7. Air velocity/volume
Drying Time (Mins)
5 10 15 2 0 25 30
0
0.5
0.7
0.9
1. 1
1. 3
1. 5
1. 7
Air Velocity (m/s)

— Circular Airflow 0.63 m/s
— Center Airflow 0.9 m/s

An increase in velocity will significantly decrease drying time and dramatically effect dryer
operations.

moisture of 7%, and the acceptable product moisture is 9.5%. This
represents a tolerance of 2.5%. The most common reason for operating
at such a high tolerance is to compensate for moisture variance in the
final product due to inconsistency in the dryer. What would happen if
technological advancements reduced the process tolerance, allowing the
process to operate with a target product moisture of 9%?
Now, that same process enjoys one or more of the following economic
benefits:
Increased production; ■
Increased revenue (unchanged production rates); ■
Reduced utility costs ■ .
In a case study involving a producer of aquatic feeds, a reduction of
moisture tolerance by 2% corresponded to a direct revenue increase of more
than US$300,000 in the first year, with no change in product rates by simply
selling more water.

Look at the system as a whole
The focus in developing a flexible processing system is primarily
concentrated on the extrusion components, and the drying has become
more of an afterthought. It pays to look at the system as a whole.
At Extru-Tech, we know those companies willing to discuss their
operational goals and discover advancements in drying technology, such
as the AirFlow II, can see increases in moisture management, production
capabilities and, ultimately, return on investment profits.
■