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Internal Waste Heat Utilization

Heated adsorption dryers use thermal energy to desorb moisture from the adsorbent, typically requiring heating temperatures as high as 150℃ or more. After moisture desorption is complete, the adsorbent is in a high-temperature state and must be cooled to restore its ability to adsorb moisture. Therefore, waste heat is generated during the cooling stage.
If the waste heat generated in the internal regeneration process of an adsorption dryer can be effectively utilized, significant energy-saving purposes can be achieved.

Internal waste heat utilization can be classified into two main types according to the cooling method:

(1) Cooling using compressed dry air
(2) Circulating cooling using heat exchange

The heating and cooling directions of the regeneration process are designed to be the same. During desiccant regeneration, hot air of about 200℃ is used to desorb moisture layer by layer (key point). After calculation and confirmation that heating can be ended early, the air volume in the initial stage of cooling is used to carry out waste heat to compensate for the thermal energy lost due to the shortened heating time. This action saves heating energy consumption because the heating time is reduced.
Typical heated air-cooled dryers can save more than 20% of heating power consumption using this method.

The heating and cooling directions of the regeneration process are designed to be the same. During desiccant regeneration, hot air of about 200℃ is used to desorb moisture layer by layer. When the heating desorption process is about 50% complete, the heating temperature is lowered from 200℃ to about 120℃ for the second stage of sub-high temperature heating. This 120℃ sub-high temperature heating airflow carries the 200℃ hot air upwards to desorb the remaining desiccant.
Utilizing sub-high temperature heating reduces the energy consumption of the heater because the temperature decreases in the later stage of the heating process, but the outlet quality of the compressed dry air must be noted. If the dew point quality does not meet the requirements, the temperature of the second stage sub-high temperature must be gradually increased until the outlet quality of the compressed dry air meets the requirements.
In the above heating process, the temperature rise value of the heater in the second stage sub-high temperature is only about 50% of that in the first stage heating, so heating energy can be saved. During cooling, it also cools down from 120℃ instead of the original high temperature of 200℃, which means that this method can achieve the advantage of bidirectional energy saving in heating and cooling.