Corrosion Evaluation of SS316L Amine/Amine Plate Heat Exchangers of the SPGC Ethane Refining Units

Ethane treatment process unit of the South Pars Gas Complex (SPGC) includes sweetening the gas by absorption of acidic gasses with Di-Ethanol Amine (DEA). In this process, hot lean amine discharges from a regenerator tower, pre-heats the rich amine by a Plate Heat Exchanger (PHE) with 316L stainless steel plates. According to the SPGC operation records, there was a noticeable decrease in the PHE performance which caused its isolation for inspection. The primary visual inspections revealed a significant scaling on the rich amine sides of the 316L plates. Hence, chemical composition of the scales was analyzed and iron oxide was detected as the predominant compound. Also, the Penetration Tests (PTs) revealed a severe pitting corrosion on the gasket seats. The pitting morphology and mechanism were investigated using StereoMicroscope (SM), Scanning Electron Microscope (SEM), and Atomic Force Microscope (AFM). In addition, the gasket glue was analyzed using Fourier Transform Infrared Spectroscopy (FTIR) to find the halide compounds. Results showed that the chlorine ions have been extracted from the gasket glue and caused pitting corrosion. Besides, residual stresses of the cold worked plates have been activated the Chloride Stress Corrosion Cracking (CLSCC) mechanism which the micro-cracking has been initiated from the bottom of the pits and then the micro-cracks have been propagated through the grains and along the grain boundaries of the 316L plates.

کلیدواژه ها:

Plate heat exchanger ، Amine service ، Pitting corrosion ، CLSCC ، Chlorine ion