What's the difference between atm distillation columns and vacuum distillation columns and why we use vacuum distillation?

The atmospheric distillation column is used to handle the straight crude oil and it operates at a pressure of roughly1 atm. The vacuum distillation column is used to handle the residue (being heavy) from the distillation column and that at a reduced pressure in order to decrease the boiling point of the species so that the recovery of heavier components can be done easier.

in vaccume distilation the column iis usually of larger diameter and below the atmosperic pressure while in an atmospheric distilation the column is usually of small diameter and on or above the atmospheric pressure

The main difference between them pressure, atm distillation operate at atmospheric pressure and vacuum distillation operate negative pressure, it is used for that product who have higher boiling point so it can easily recovered at low temperature.

 

   

ATM  Pressure at distillation column is a positive pressure and Vacuum pressure is a negative pressure.

We use the vacuum pressure to reduce partial pressure for each component which involve the reduction of the boiling temperature for each component. Heavy products being evaporated easily.

 

The main difference is the pressure, In atm. distillation the pressure is atmospheric or above and used for normal compounds such as fresh crude oil where the separation is done at normal boiling point. While in vacuum distillation the pressure is below atmospheric pressure and used for the heat sensitive compounds such as residual crude oil from atm. distillation where the separation happens at resided boiling point

Distillation column are typically operated to separate multiple components to specific by it's various boiling points to separate specific components,distillation column are utilized to separate different components(molecules) by specific boiling point, here most of components are separated without any physical changes at atm distillation column but some may crack to light molecules by the operating temperatures it goes beyond the critical temperature, but we required to achieve by cost effectively about to size and volume of the column and without any crack, by reducing the operating pressure and temperature are achieved by reducing it's boiling points  by vacuum distillation column.

   .(Vacuum distillation is under atm pressure ( Below  101.3kpa )   we use this process to separate  materials need high temperature to avoiding cooking . normal distillation under pressure to separate any materials  not need high tempreature

Atmospheric distillation column is used to separate the crude oil components into its fractions which are valuable products like gasoline, LPG, kerosene, Diesel fuel, naphtha and heavy gas oil. It operates at approx 1 atm. The basic principle used in ADU is fractional distillation (distillation on boiling ranges).Vacuum distillation column is used to separate residue, bitumen, petroleum wax. Since at higher temperatures, cracking of residue takes place, vacuum is used to lower the boiling points of the fractions being distilled. It operates at 40-50 mmHg.

The distillation is phenomena of relative volatility if relative volatility difference of compounds to be separated are larger at atmospheric or above atmospheric pressure then this method is used for separation if relative volatility difference is higher at below atmospheric pressure than Vacuum distillation is used.

 

The atm distillation columns works under normal atmospheric pressure, while the vacuum distillation is a method of distillation 

when the pressure less than the atmospheric pressure .

 

The difference is the pressure of the column. In vacuum distillation, pressure is decrease to achieve separation of the distillate from the feed at lower temperature than it is in the atmospheric distillation. Thus, less heat is required in the process.