Activated Carbon Type Selection to Reduce DEA and MDEA Foaming Tendency and Foam Stability

Amine filtration that usually includes particulate and carbon filter is one of the critical processes of a sour gas sweetening unit that ensures low foaming tendency of amine. Activated carbon adsorption bed is crucial to remove hydrocarbon and surfactants e.g. lube oil, corrosion inhibitor. However, based on empirical analysis and field data, type of activated carbons selection must be carefully performed for the specific amine solution and selected antifoam agent, rather than by-default selection of commonly used carbon types e.g. bituminous carbon. Moreover, removal of surfactants, such as antifoam from amine does not necessarily reduce foaming tendency for all amine types. The aim of the paper is to identify the effectiveness of various activated carbon types on circulated DEA and MDEA solutions, as well as impact of removal antifoam agent on the foaming tendency and foam stability. Bituminous and coconut shell activated carbon samples were used for the laboratory tests. The activated carbon type selection for DEA and MDEA was based on amine foaming tendency and foam stability e.g. total suspended solids, foam height and collapse time, and solution opacity. Numerous laboratory tests confirmed higher effectiveness of bituminous activated carbon for DEA and coconut carbon for MDEA. Also, it was noted that removal of polyglycol antifoam agent from MDEA e.g. by bituminous carbon does not result in lower foaming tendency and foam stability. Therefore, careful examination of activated carbon type for specific amine solution is required to ensure required amine solution quality. It is widely known that removal of antifoam positively affects amine foaming tendency. However, the current study indicated that the rule does not apply for all amine solution types and the selection might need special evaluation to avoid process upsets.