Which statement correctly describes the vacuum tower's purpose?

• A. Reduce boiling point so you don't have to heat as much to boil
• B. Increase boiling point for tighter separation
• C. Remove water from crude
• D. Store heavy residues

Answer: (A)

The vacuum tower works by reducing the pressure inside the column, which lowers the boiling points of the liquids being distilled. By operating under vacuum, heavy hydrocarbon fractions can vaporize and separate at much lower temperatures, preventing thermal damage such as cracking or coke formation that would occur at higher, atmospheric temperatures. This makes the separation of heavy components like vacuum gas oil and resid more energy-efficient and improves product quality because you don’t have to heat them to extreme levels to achieve vaporization. It’s not about removing water from crude (that’s the desalter’s job), nor about storing heavy residues, and it doesn’t increase boiling points—the point is to lower them through reduced pressure so distillation is possible at gentler temperatures.