Experimental study of erosion in a high-temperature fluidized bed with granular materials for concentrated solar power applications

Abstract

Interest in concentrated solar power plants using fluidized solid particles is growing because they offer several advantages, namely, the use of a renewable energy source, the use of the same power cycle technology that conventional fossil fuel power plants or energy storage capabilities. Nonetheless, the use of solid particles means that heat exchangers or internal devices are exposed to a highly erosive environment.

This experimental study assesses the evolution of the erosivity of a fluidized bed with fluidization velocity and temperature using bars made of aggregated calcium carbonate immersed in a laboratory-scale fluidized bed of particles suitable for concentrated solar power applications: silica sand and silicon carbide. The mass loss after a given exposure time was measured to obtain a set of experimental data under different temperature and fluidization velocity conditions. Then, the circumferential-averaged erosion rate was estimated.

In the case of silica sand, erosion at 100 ℃ was consistently minimum for each fluidization velocity, suggesting a change in the fluidization regime. In the case of silicon carbide, the results point to changes from bubbling to slugging and bubbling to turbulent transitions at low temperature (rounding 100 ℃) and around 400 ℃, respectively. On average, the erosivity of silicon carbide was up to two orders of magnitude higher than that of silica sand. For instance, at 20 ℃ and under similar bubbling fluidization velocity, the erosion rate of silicon carbide was $482\mu m$/h, while that of silica sand was about $3\mu m$/h.