51312-01333-Corrosiveness of DIPA/Sulfolane Mixtures Under Gas Treating Conditions

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Product Number: 51312-01333-SG

ISBN: 01333 2012 CP

Author: Gerit Siegmund

Publication Date: 2012

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The removal of CO2 and/or H2S from natural gases is frequently performed by treating these gases with mixtures of diisopropanollamine (DIPA) and sulfolane. These solvent mixtures absorb the acid constituents and thus clean the natural gases. During the technical absorption process obviously critical conditions can exist which cause HIC and general corrosion at the low alloy steels of absorber columns. Technical observations raised suspicion that the loading intensity of the solvent mixture with H2S and CO2 plays the leading role. This paper reports on rotating cage experiments with steel coupons from a corroded absorber column using as corrosion medium i) technically used DIPA/sulfolane mixtures from an absorber column and ii) newly prepared DIPA/ sulfolane mixtures with different sour gas loading for each liquid. At 85 °C and 5 m/s circumferential speed of the rotated coupons the general corrosion rates ranged between 0.1 and 0.2 mm/y in case of newly prepared (fresh) DIPA/sulfolane mixtures nearly independent of the loading ratio. However in technically used DIPA/sulfolane mixtures the corrosion rates depended significantly on the loading ratio and ranged between 0.02 to 0.5 mm/y. A threshold value was found for the loading ratio above which the corrosion rates increased by one order of magnitude. The different corrosion behaviour of freshly prepared and technically used DIPA/sulfolane mixtures respectively manifests itself by formation of different sulfide scale morphologies. Mechanistic considerations are discussed.