Use of Activated MDEA for Acid Gas Removal

When the MDEA process was developed in the mid-1970s it was principally destined for the sweetening of gases that did not require complete CO2 removal [ 1 ], or required the removal of only a controlled part of the CO2. Typical applications of the selective MDEA process are  

The basic concept for a new process was then to take advantage of the slope of the equilibrium solubility curves of CO2 in aqueous MDEA solutions to be able to liberate a maximum amount of the acid gas from the solution by simple physical 

With MDEA alone the transformation of CO2 into bicarbonate is a slow process while the reaction of the carbonic acid with M D EA is instantaneous. With an activator in the MDEA solution the transformation into bicarbonate via a first step formation of 

When H2S is present and the treated gas specification calls for the removal of H2S below 3.0 ppm, or for the removal of CO2 below the l-2vol.% range, thoroughly regenerated, virtually H2S- and C02-free, amine is required. This is accomplished in a conventional thermal regenerator by returning a small flow of the leanest amine to the top section of the absorber. 

In 1990 the new solvent and regeneration system were tested on an existing DEA unit at Lacq, which was then converted into the then-called Elf Activated MDEA process [3,4]. This process was also used in several other locations offshore North Sea such as in Sleipner Vest for CO2 removal and Elgin Franklin for controlled CO2 removal. Different activators have been selected and patented to suit each specific case of treatment total or partial, controlled CO2 removal with or without H2S. 

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