Knock out drum (KOD)

EEI has designed, manufactured and supplied several knockout drums for oil field system of national and international customers. The maximum efficiency achieved by the EEI knockout drum and mist eliminator configuration is 99.96 %.

A knockout drum is a vertical or horizontal vessel used upstream of the flare to remove any liquid that may accompany the relieved gases and is used to separate the entrained droplets from vapour stream. In most industrial plants, there is a vapour-liquid separator or knockout drum.

Sizing a knock-out drum requires experience and good knowledge of the process. Drum size is based on the Liquid particles, vapor or gas. The vertical height is decided based on the dropout velocity of the liquid particles, and the vertical gas velocity which should be sufficiently low for the liquid droplet to fall. Horizontal and Vertical vessels are chosen based on the volume of the gas oil and water mixture

By selection of sufficiently large vessel diameter, the gas velocity in the vessel can be kept low and the majority of the droplets will settle by gravity. Gravity causes the liquid to settle to the bottom of the vessel, where it is withdrawn. Generally, gravity settling removes 90% of the liquid entering the vessel. The vapor travels upward at a designed velocity which minimizes the entrainment of any liquid droplets in the vapour as it exits the top of the vessel. Only when not more than bulk separation is required and the droplets are relatively large the separation internal can be omitted, the remaining droplets smaller than 380 microns can be a significant problem for a downstream unit. This separation mechanism is used in knock-out vessels.

The feed to a vapour-liquid separator may also be a liquid that is being partially or totally flashed into vapour and liquid as it enters the separator.

knockout drum is suitable for bulk separation of gas and liquid.

A vapour-liquid separator may also be referred to as a flare KO drum, flash drum, knock-out drum, knock-out pot, compressor suction drum or compressor inlet drum.

It is often necessary to separate liquid and gas phases in a certain stage of an operation or process. Since both the conditions of the wet gas stream (or more generally the gas/liquid stream) and the required efficiency may vary widely, care shall be taken in selecting a separator in order to match the specific duty.

A knockout drum with a mist eliminator is common whenever a process requires entrained droplets to be separated from vapour stream. After passage through the feed inlet, the gas stream will usually still contain the liquid in the form of droplets. Normally further internals is required in the vessel to complete the separation process.

A simple knockout drum (without a mist eliminator) will remove droplets larger than about 380 microns by gravity settling.

A mist eliminator at the top of the knockout drum will remove the droplets down to a diameter of 6 microns or less, depending on the dryness required. When used to remove suspended water droplets from streams of air, a vapour-liquid separator is often called a Demister.


Difference between Flash vessel and knockout drum

Flash Vessel is a 2-way separator of steam and water.

Knock out Drum is a 3-way separator of oil, gas/ steam, and water.

Flash Vessel is installed anywhere upstream of the boiler. Knock out Drum is the last equipment before flaring. with the following details for techno- commercial offer
Medium to be separated- flow, pressure, temperature