Investigation of Batch Distillation Operating Modes

Distillation is a method of separation using a column and involves heating a mixture of liquid components with differing boiling points. As the mixture is heated, the components vaporize and condense on trays along the height of the column as they cool. Distillation has a long history dating back to ancient Mesopotamia and Egypt as a method of perfume and medicinal compound production. It has since advanced to meet specifications through fractional distillation. Three experiments were performed to better understand pressure drop along the length of a column, column efficiency under total reflux, and column efficiency under constant reflux. This was done by varying the power to the reboiler of the column bottoms, or varying the reflux ratio and measuring the pressure drop via manometer, and obtaining overhead and bottoms samples. The Darcy-Weisbach equation was used to correlate the boil-up rate to pressure drop. The Fenske equation was used to determine the minimum number of trays needed to obtain a given composition under total reflux. Under constant reflux, a similar analysis was completed using a McCabe Thiele diagram. It was found that the pressure drop increases with boil-up rate, however, not with the relationship predicted by the Darcy-Weisbach equation. The operating mode, boil-up rate, and reflux rate had no impact on the number of trays needed to obtain a given composition. Additionally, a design extension was provided to show how distillation can be used for the production of spirits.