Temperature
that relate drying time, moisture
The required air temperature for any drying process is defined by product
and air temperature).
characteristics and raw material components. For true capacity efficiency
Figure 1 shows a drying
(which is most common), the temperature should be operated at a highest
time of 11.8 minutes with an air
acceptable level for a specific product. It is important to note that this level
temperature of 90°C. Figure 2
will depend on product specifications and equipment configuration.
shows that if the air temperature
With the temperature optimized, other drying parameters can be
is optimized to 115°C (a 28%
manipulated into an economically favorable set of operating ranges. Figures
increase), the drying time is
1 and 2 (see p. 4) are examples of product-specific drying curves (graphs
reduced by 42% to five minutes.

Dryers: hands on … coming in the next issue of
This is important because now

Figure 3. Direct comparison
the remaining control parameters
can be tailored to meet your
specific process requirements.
Learn about
procedures that:

5 10 20 30 0
Drying Time (Mins)
15
25

Drying Temperature °C

Combining the drying curves from Figures 1 and 2 (p. 4) allows for a direct comparison
between drying time and air temperature.

Some operating options that may
now be available (depending on
system configuration) include:

Increase in extrusion capacity,
decrease in drying time.
To further demonstrate the
interdependency or parameter bias,
these items will indirectly affect bed
depth and product moisture.
Figure 3 combines the drying
curve examples of Figures 1 and
2 to show a direct comparison of
drying time to air temperature. ■
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