How to Reduce Process Heat Loss

Latest Energy Saving Technologies

There are two types of dryer manufacturers- one who advocates energy savings and the others who do not consider saving energy an important task primarily because they lack testing facilities or are not qualified enough to conduct testing. However, the chart of Energy Costs of Old vs. New Dryers will help you understand the value of energy saving while employing drying parameters.

The charge shows the current average energy costs and after a quick glance, you will clearly understand why latest energy saving technologies is a boon for the business. This simply means that the bigger the dryer, the greater will be the savings and thus you will get a better ROI.

The performance of any drying system can be analyzed on its ability to maintain the appropriate drying temperature as well as maintaining a constant material temperature at the throat of the injection molding machine or extruder, utilizing minimum heat. The regeneration system of the machine should also contribute to energy saving by directing most of the energy to remove the moisture gained during the drying process.

How to reduce the process heat loss utilizing latest energy saving technologies:

Most of the times, dryer manufacturers trick you in the name of energy saving claims. They would claim Temperature Setback or Second Set Point as energy saving features but actually, they aren’t one. Temperature setback is more frequently used than a second set point, let’s understand what it is?

Temperature Setback controls the process temperature and maintains it low which ultimately affects the resin temperature entering in the processing equipment. This provokes that machine to have lower heat in the resin by increasing the heat from shear and the band heaters. Ultimately, the processing machine ends up using more energy to overcome the shortcomings of the dryer and thus no energy will be saved.

Another technique that is used for energy savings is VFD’s (variable frequency drives) to control process blower speed. The concept behind this process is to minimize the required air level in order to keep the energy level required for process heating to the minimum.

The complete function can be understood through the following image:

Dryer Plastics Process Heat Savings Diagram
Figure 1- Controlling the temperature of the air exiting the hopper reduces heat loss and increases energy savings. Image courtesy of

Reducing Regeneration Heat Loss:

Approximately 35% of the total power used is employed in regeneration. To ensure that you are working towards your goal of energy saving you must keep the power usage at the desiccant to the minimum. In the process of regeneration, the desiccant is heated to a certain temperature where it releases the moisture gained during the resin drying process.

The entire system has two parts: we will understand it through a desiccant wheel dryer model

The first step is to minimize the speed (RPM) of the desiccant wheel. This plays an important role because if the desiccant media becomes hot it would deviate from its primary goal to eliminate any type of vapor and heat will be lost. With the help of variable frequency drive (VFD), the heat is maintained to the point that it is enough to absorb the moisture from the return air.

The second step is done at the regeneration air blower using a VFD. Here the VFD ensures that the water is desorbed from the molecular sieve with minimal energy use.

This entire process can be best understood by the following figure.


Dryers Plastics Process Regen Energy Savings
Figure 2- Controlling the regeneration blower speed and the desiccant wheel speed reduces regeneration heat loss and increases energy savings.
Image courtesy of
Toyo 250ton molding machine

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