De-ethanizer reboilers in a Natural Gas Liquid Fractionation (NGLF) plant fouled repetitively. Samples of deposited sludge were collected and analyzed. Results of the sludge samples analyses reveal a chemical composition typical of black powder: Magnetite (Fe3O4), Goethite (γ-FeOOH) and trace amounts of Quartz (SiO2). By process of elimination, pipeline loops were the suspected source of these solids. The results show that Fe3O4 is the main component which normally originates in these cases from a process of dissolved oxygen corrosion due to the presence of very small amounts of oxygen and water in the pipeline. The presence of oxygen and water in the pipeline could be due to the exposure of the pipeline to the atmosphere during pipeline construction or other major repairs. Silicon dioxide (SiO2) is a natural compound of silicon and oxygen found mostly in sand which again could enter into the pipeline during construction or major repairs. For comparison and possible new insights, results of previous studies conducted internally were also reviewed. Based on identified types of corrosion and chemical reactions products, a reversed sequence of events was reconstructed. The main corrosion mechanisms proposed are oxygen corrosion, under-deposit corrosion, and microbiologically-influenced corrosion (MIC), as well as erosion of mill scale by sand particles. The laboratory analyses were conducted using X-Ray Diffraction (XRD), Wavelength Dispersive X-Ray Fluorescence (WDXRF) spectrometry, Thermogravimetric Analysis (TGA), and Environmental Scanning Electron Microscopy integrated with Energy Dispersive X-Ray Spectroscopy (ESEM/EDS).

Subject
X-ray diffraction, Chemical compounds, Water, Sand, Solids, Pipelines, Minerals, Contaminants, Sludge, Reboilers, Magnetite, Oxygen, Samples
Keywords:
black powder, natural gas liquid fractionation (NGLF), pipeline corrosion
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2021
Association for Materials Protection and Performance (AMPP)
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