An Industrial Methodology for Erosion Analysis of FCC Expander Blades

Abstract Fluid Catalytic Cracking (FCC) is a process for the conversion of heavy stocks recovered from different refinery operations into high-octane gasoline, light fuel oils and olefin rich light gases. Zeolite particles are used as catalyst in the process to facilitate the cracking of long hydro-carbon molecules. Because of the contact between catalyst and feedstock, coke deposits on the catalyst active surface reducing its activity, air is used to remove it from the catalyst, in the regenerator. The coke burning produces a hot flow of flue gas with a valuable energy content (700°C – 3bar) that can be recovered using a Hot Gas Expander HGE before releasing the exhausts in the atmosphere. The flue gas is carrying a certain amount of catalyst so the expander hot parts (mainly blades but also the stator vanes) are constantly exposed to an abrasive medium that may compromise the reliability of the asset. Understanding how the solid particle erosion works is one of the challenges that HGEs designer shall deal with. To this purpose, a numerical approach was developed to account for some of the factors that are known to play a major role in erosion phenomena: particle velocity, angle of impact, composition and particle size, as well as the mechanical properties of the target surface at the operating temperature. The methodology was then applied to a cascade blade for which erosion data collected in a stationary erosion test rig are available. The comparison between numerical and experimental data showed a good agreement therefore providing confidence on the proposed methodology. Finally, the numerical procedure has been applied to a real case to show the effect of the different catalyst load on the life of the blades.