Installation of atmospheric-vacuum distillation of oil

The K-1 topping column is part of the AT installation with double evaporation of oil (Figure 2.1). This scheme is technologically flexible and workable for any fractional composition of oil. Due to the removal of light gasoline fractions in the furnace coils in the K-1 column, high pressure is not created in the heat exchangers and the main column K-2 is not overloaded with vapors [6].

Figure 2.1 - Schematic diagram of the AT oil distillation installation

Dehydrated fresh and desalted oil by pump 8 is fed into boiler 6, heated to 220–230 °C, after which it is fed into the K-1 distillation column, where the light fraction of gasoline and gas are collected. The unevaporated residue flows into the lower part of the column through plates. The vapor flow from the evaporation space of column 1 is mixed with the vapor flow stripped from semi-stripped oil and sent as reflux to the upper part of column K-1. On each plate, due to the contact of the cold reflux flowing from the top of the column with the ascending flow of vapor, heat and mass transfer occur; the vapor, when moving upward, gradually becomes lighter on any higher plate, reaching a given quality on the upper plate. As a result of this, approximately half of the gasoline fraction with a boiling point of 130–140 ° C is removed, which is condensed and cooled to 40–45 ° C in condenser-refrigerator 3 and, after mixing with a heavier gasoline fraction from column K-2, is sent for stabilization (removal dissolved gas) and then to secondary distillation. 

The heavy part of the vapor condenses on each plate and enriches the reflux with high-boiling components. After passing through all the plates in the lower part of the column, the watery residue reaches a given composition in terms of the content of low-boiling fractions (for fuel oil - no more than 4–6%). In practice, these are fractions with a boiling point below 360 °C.

Superheated water vapor supplied to the bottom of the column reduces the partial pressure of oil vapors and strips low-boiling elements from fuel oil. Water and gasoline vapors leave the top of the column with an end boiling point of no higher than 180–190 °C. Regulation of the quality of products based on the end boiling point is carried out by supplying gasoline reflux by returning part of the upper product of column K-2, cooled and condensed in the refrigerator-condenser 3. This maintains a certain temperature of the vapor leaving the upper plate and the quality of the gasoline fraction. Side streams of other petroleum products in watery form are taken from the underlying plates of the concentration part of the column. The high side is the kerosene fraction, lower is the light diesel fraction, and even lower is the heavier diesel fraction.