Explain the relationship between the degree of vacuum applied in a vacuum distillation unit and the prevention of thermal cracking of the residue.

The degree of vacuum applied in a vacuum distillation unit is directly related to the prevention of thermal cracking of the residue. A vacuum distillation unit operates under significantly reduced pressure compared to an atmospheric distillation unit. The purpose of applying a vacuum is to lower the boiling points of the heavy hydrocarbon components in the residue, allowing them to vaporize at lower temperatures. Thermal cracking is the breakdown of large hydrocarbon molecules into smaller ones due to excessive heat. If the vacuum is insufficient, higher temperatures are required to vaporize the residue, which increases the risk of thermal cracking. This is because the boiling ....