Rectification column: how the “molecular skyscraper” works
Imagine that liquid molecules with different boiling points are passengers going up or down a staircase. In the reboiler, the mixture is heated at the bottom of the column: light molecules turn into steam and move upwards. At each plate or nozzle, the steam meets the cooled liquid, where some condenses and evaporates again, gradually purifying itself. In the condenser at the top, the lightest molecules cool down and form a pure distillate, while the heavy ones remain at the bottom.
The temperature gradient (from ~200 °C at the bottom to ~30 °C at the top) controls the direction of movement of the molecules.
Due to the repeated contact of steam and liquid, the purity of the product gradually increases.
This is how pure alcohols, solvents, and petroleum products are obtained in industry – no magic, just a delicate balance of mass transfer and thermodynamics!