Determination of sulfur in corrosion products by X-ray fluorescence analysis as a method of assessing the integrity of oil refinery equipment

The analytical capabilities of wavelength-dispersive X-ray fluorescence spectrometry (WDXRF) for determination of total sulfur content in corrosion deposits formed on oil refinery and petrochemical processing equipment are evaluated to prevent equipment failures. Deposit samples collected from diverse process equipment exposed to corrosive environments have been analyzed. The total sulfur content was determined using the standard-free method of fundamental parameters and calibration dependences plotted at the reference samples analysis using regression models. Samples of corrosion deposits of technological equipment containing iron sulfides and sulfates were taken as reference materials. The sulfur content in them was determined gravimetrically. A preliminary study was conducted to estimate the influence of other sample components on the results of sulfur determination. It was found that when plotting calibration dependences, it is necessary to take into account not only the concentration of Fe (matrix), but also the other significant elements such as Ca. For the correct sulfur determination its prevalent valence form should be also considered: sulfate form is confirmed by the satellite SK β’ peak in XRF spectrum. The developed technique allows the express monitoring of equipment at oil and gas facilities predicting remaining service life, and evaluating operational risks.