As outlined in the post on process design the microstill recycles the heat. The hot product vapor condenses in the heat exchanger and the wash is preheated. The energy is transferred from the vapor to the fresh wash. No additional coolant is required. The wash serves as coolant. What interested me is the balance between energy that is absorbed by the fresh wash (heat capacity) and the energy required to form the product vapor (vaporisation enthalpy).
The results are summarised in the graph. The assumption for the calculation are: freh wash at room temperature of 20 °C that will be heated up to 97 °C. A part of the wash will be vaporised until reaching that temperature. This is not considered.
Depending on the wash ABV the heat capacity decreses (blue). This is due to the lower heat capacity of ethanol. The higher the ethanol content the lower the heat capacity.
In contrast the vaporisation energy increases steeply (red). This is due to the increasing alcohol content. The more ABV in the wash the more alcohol will be vaporised. For each point the ABV of the product have been added. A wash of 5 %ABV will yield a 35 %ABV product. Per L of wash additional 200 kJ need to be added by electrical heating

Leave a comment

Your email address will not be published. Required fields are marked *