Gas liquid contacting devices are used widely in the chemical industry for absorbing gases into liquids and solvents. These devices range from stirred vessels to packed beds and bubble columns and are employed for a variety of different industrial applications, including CARBON CAPTURE FROM AIR.

Most applications employ an upflow mode of gas flow with relatively low gas hold-ups (< 20%) along with subsequent gas disengagement with recycling, coalescence and backmixing problems. Free gas liquid interfaces with gas pockets are formed in these reactors causing safety problems. Furthermore downflow bubble columns usually operate with jet entrainment of gas and gas bubbles therefore require subsequent disengagement and uneconomic utilisation of gas whilst the interfacial area is not optimised.

The DGC offers significant advantages over more conventional gas-liquid contacting devices and is able to achieve saturation in very short reaction times. Some of the advantages of the DGC when compared with other contacting devices are highlighted below.

See some graphical comparisons of the Downflow Gas Contactor.

DGC compared with a stirred tank for an oxidation process

Process Conditions

Operating Temperature 15°C
Liquid Flowrate 10 m3/hr
Initial Dissolved O2 Conc. 10 ppm


Stirred Tank DGC
Operating Pressure (Bar a) 5 4
Contact Time (seconds) 300 10
Approach to Equilibrium (%) 62.5 96
Gas Utilisation (%) 90 100
Outlet O2 Conc. (ppm) 150 150
Volume of Adsorption Equipment (m3) 1.5 0.05
Power Absorbed (kW) 4.8 1.2

Bubble Dispersion in the DGC

DGC compared with a Spray Column for a Carbonylation process

Process Conditions

Operating Pressure 5 Bar
Liquid Flowrate 10 m3/hr
Initial Dissolved CO2 Conc. 10 ppm


Spray Column DGC
Operating Temperature (°C) 5 15
Hold up Time (seconds) 80 24
Approach to Equilibrium (%) 70 97
Gas Utilisation (%) 100 100
Outlet CO2 Conc. (ppm) 9500 9500
Saturation CO2 Conc. (ppm) 13500 9640
Volume of Adsorption Equipment (m3) 0.2 0.06
Absorption Energy Ratio (kg/Wh) 0.5 1.4

Inlet of a slanted DGC Reactor