Hydrogen Diffusion Corrosion Problems In a Fluid Catalytic Cracker And Gas Plant

An account is given of corrosion problems in a fluid catalytic cracker and gas plant following a 19,000 hour run. Specific places where corrosion damage occurred and was examined include: (1) the carbon-moly steel reactor, (2) the regenerator, (3) catalyst lines, (4) the gas plant. It was found that corrosion became a problem when coupled with erosion in cyclones or diffuser grids. Alloying could not be justified except on stressed parts. Hydrogen blistering was discussed in detail. It was found that its occurrence in the gas plant was a function of pH downstream of the water wash tower. As the pH increased in the absorber deethanizer, so did the hydrogen penetration rate. Control measure finally adopted to mitigate hydrogen blistering included recording of hydrogen probe pressures, pH of draw waters, analysis of wash water, and iron content of draw waters. Ferrocyanide spot tests were also made and inhibitors were tried. 8.4.2