Atmospheric distillation

Principle

The oil passes through heat exchangers, a desalter and a tube furnace, where it is heated to 350–360 °C. The vapor-liquid mixture enters the distillation column, where, due to the contact of vapors and flowing reflux, separation into fractions according to boiling points occurs.

Above 370 °C, the thermal decomposition of hydrocarbons begins, so heating is limited, and the heavy residue is removed from below and sent either to vacuum distillation or to commercial fuel oil.

Products

• gasoline fraction (naphtha) - approximately n.c. – 180 °C;
• kerosene fraction - 180–240 °C;
• diesel fraction - 240–350 °C;
• fuel oil - residue above 350 °C.

The boundaries of the fractions are set by the technological regime and the requirements for the target product, so they differ in different installations.

Hardware design

The main elements of the installation: a tubular furnace, an atmospheric column with stripping sections, heat recovery heat exchangers, air and water coolers, irrigation tanks. The typical circuit is called AT; if there is a vacuum unit - AVT.

Restrictions

• the process does not change the chemistry of hydrocarbons: the quality of the products is determined by the quality of the oil;
• the gasoline fraction after distillation has a low octane number;
• sulfur and highly paraffinic oils require separate solutions - hydrotreating, dewaxing;
• The yield of light distillates on atmospheric distillation is limited by the content of fractions in the raw material.