Distillation Column

Overview

The distillation column is the central separation unit of a refinery crude unit. It splits desalted, preheated crude oil into product cuts by boiling point: overhead naphtha and light gas, kerosene and diesel side draws, and a heavy atmospheric residue from the bottoms. Crude enters partially vaporized in the flash zone and the lighter fractions rise as vapor while the heavier liquid falls, with each tray or packing layer acting as an equilibrium contact stage.

A full column is more than the tower: it includes the heat-input and heat-removal equipment, the accumulator that sets reflux, and the pumps and instrumentation that hold the cut points steady against changing crude quality.

How it works

Hot feed flashes in the lower section; vapor rises through the Column Internals, where valve trays in the upper rectifying zone and structured packing beds lower down repeatedly condense and re-vaporize the stream so each component concentrates at the tray matching its boiling point. The pressure-bearing Column Shell carries these internals across stacked cylindrical courses, with nozzles for the feed, side draws and instruments.

Bottoms liquid is partially vaporized in the Reboiler, a kettle exchanger that returns stripping vapor to the base. Overhead vapor passes to the Overhead Condenser, where cooling water liquefies it; the condensate collects in the Reflux Drum, which separates net product, reflux and any water boot draw. The Pump Skid return reflux to the top tray and move bottoms and side-draw product downstream.

Cut points are held by the Instrumentation package: differential-pressure level transmitters, a tray temperature profile, and orifice flow loops feed DCS controllers that modulate reflux, reboiler duty and draw rates through the Piping & Valves control valves. Spring-loaded relief valves guard against overpressure. The Access & Structure platforms and caged ladders give maintenance crews reach to every manway elevation along the 52 m tower.