Vacuum distillation

Why do we need a vacuum?

Fuel oil at atmospheric pressure cannot be heated above 370–380 °C without cracking: molecules begin to break down, products become tarred, and coke contaminates equipment. At a residual pressure of the order of several kilopascals, the boiling point of the heavy fractions decreases by tens of degrees, and the separation occurs within a safe range.

Products

• vacuum gas oils - raw materials for catalytic cracking and hydrotreating;
• light and heavy vacuum gas oil as components of commercial products;
• tar is the residue used for bitumen production, deasphalting or coking.

Equipment

Key components: vacuum column with packing or trays, vacuum system (steam ejector or liquid ring pumps), furnace with reduced thermal load, condensers. The mode is sensitive to air leaks and overheating of the bottom of the column.

Connection with bitumen production

The depth of gas oil selection determines the properties of tar: the more selected, the denser and harder the residue. That is why a vacuum unit is often designed together with a bitumen installation - for the required brandbitumen.