The Antoine equation

The boiling point readout uses the Antoine equation for ethanol from the NIST Chemistry WebBook: log10(P) = A minus B divided by (T + C), with P in bar and T in kelvin, and A = 5.37229, B = 1670.409, C = minus 40.191 (Kretschmer and Wiebe, valid from about 273 to 352 K). Solving for T gives the temperature at which ethanol's vapor pressure equals the pressure you set.

The recovery rate is a simplified heat transfer estimate, not a manufacturer rating: heat flow = U times A times the temperature gap, divided by ethanol's heat of vaporization (about 0.9 MJ per kg). It assumes a 20 liter class industrial flask with roughly 0.25 square meters of wetted glass, an overall coefficient of 400 W per square meter per kelvin, and a wetted area that grows with the square root of rotation speed.

From the lab bench to the plant

Large hemp processors often use falling film evaporators instead, where the solution runs as a thin film down the inside of heated tubes under vacuum. The physics is the same: low pressure for a low boiling point, a thin film for fast heat transfer, and a cold condenser to capture the solvent.

Keeping evaporation temperatures low protects heat sensitive terpenes and cannabinoids. Facilities treat ethanol vapor as a fire hazard, venting vacuum pump exhaust and using rated equipment, and recover most of the solvent for reuse.