Surface behavior of heat exchanger tubes in fluidized-bed combustors

Microstructure and elevated-temperature erosion-oxidation behaviour of aluminized 9Cr-1Mo Steel

“…As the layer of sand particle debris becomes continuous enough, such as at the speeds of 8.6 or 8.8 m s −1 , it evidently starts to provide the specimens 8 protection against further particle impacts, therefore leading to smaller thickness losses than at the lower speeds with more discontinuous particle debris layer. In previous studies on aluminium based diffusion coatings, deposition of sand residues on the specimen surfaces has been observed during the tests [20,[25][26][27][28], consistently with studies on uncoated steels [29][30][31][32][33] and other uncoated alloys [34], but very seldom such deposition has protected the target material against further particle impacts. Only in the cases where the erodent particles have been reported to contain soft constituents, such as Ca, S and K, formation of a homogeneous and protective layer of particle debris has been detected [35,36], with calcium compounds acting as a cement that binds the bed material ingredients together on the metal surface [37].…”

Wastage Rate of Water Walls in a Commercial Circulating Fluidized Bed Combustor

“…Metal wastage is caused by simultaneous erosion and corrosion (Wang et al, 1990;Johnson, 1991;Dutheillet and Prunier, 1998;Solomon, 1998;Nafari and Nylund, 2002). The rates and mechanisms of metal loss are complex functions of the characteristics of the particles, i.e., composition, shape, size, and strength; of the conditions inside the combustors, such as temperature, gas or particle velocity and impact angle, gas composition, solids loading, and location; and of the characteristics of the metal, i.e., composition and morphology (Wang et al, 1990). Higher wastage is associated with higher ash content and with a greater proportion of hard erosive species, such as SiO 2 , Al 2 O 3 and Fe 2 O 3 , in the coal ash (Lindsley et al, 1995;Wang and Luer, 1998).…”

“…Higher wastage is associated with higher ash content and with a greater proportion of hard erosive species, such as SiO 2 , Al 2 O 3 and Fe 2 O 3 , in the coal ash (Lindsley et al, 1995;Wang and Luer, 1998). The greater the proportion of weaker and softer limestone and the larger the CaO content, the less erosive is the bed material (Wang et al, 1990). CaO mechanically mixed with Fe oxide forms an intimate mixture that protects the metal surface (Geng et al, 1991).…”

“…Metal loss increases with increasing particle size (Wang et al, 1990(Wang et al, , 1992Rogers and Boyle, 1993). Angular particles erode metal surfaces more than round ones (Ninham et al, 1989;Zhu et al, 1990;Wang et al, 1990Wang et al, , 1992Lindsley et al, 1995). Metal wastage increases with increasing gas and particle velocities (Wang et al, 1990;Geng et al, 1991;Seitzinger, 1995).…”

“…Angular particles erode metal surfaces more than round ones (Ninham et al, 1989;Zhu et al, 1990;Wang et al, 1990Wang et al, , 1992Lindsley et al, 1995). Metal wastage increases with increasing gas and particle velocities (Wang et al, 1990;Geng et al, 1991;Seitzinger, 1995). The particles must be strong enough not to shatter upon impact in order to be erosive (Wang et al, 1990(Wang et al, , 1992.…”