Regenerated diisopropanolamine (DIPA)/sulfolane absorber liquids and freshly prepared DIPA/sulfolane mixtures exert different corrosivities for low alloy pressure vessel steel depending on the loading intensity with sour gases (H2S + CO2). The paper reports on rotating cage corrosion experiments with steel coupons from a corroded absorber column exposed in i) regenerated DIPA/sulfolane mixtures removed from process and ii) freshly 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 for freshly prepared DIPA/sulfolane mixtures, nearly independent of the acid gas loading intensity. However, in regenerated DIPA/sulfolane mixtures removed from the operating plant a threshold value was found for the loading intensity in the range between 0.74 and 0.82 mol sour gases per mol DIPA above which the corrosion rates increases by one order of magnitude from 0.02 mm/y to values above 0.2 mm/y with a maximum of 0.5 mm/y. The different corrosion behaviour of freshly prepared and regenerated DIPA/sulfolane mixtures manifests itself by formation of different sulfide scale morphologies.

Subject
Materials, Corrosion rate, Autoclaves, Steel coupons, Sour gas, Gas pressure, Mixtures, Partial pressures, Liquids, Experimental data, Steel, Gases, Alloys
Keywords:
low alloy steel, diisopropanolamine (DIPA), sulfolane, carbon dioxide, hydrogen sulfide, gas treating, corrosion
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2012
Association for Materials Protection and Performance (AMPP)
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