Comparison of Pumping Costs in Different Fluidization Technologies for CSP Applications with SiC Particles

The feasibility of using fluidized beds for thermal energy storage systems with direct radiation on the particles has been sufficiently demonstrated in several previous works. However, the focus has been placed on the useful energy stored, leaving the costs or energy losses derived from pumping particles in the background.

This work proposes to compare the pumping powers using the same material in different configurations: spout-fluid, spouted and bubbling beds. Within the bubbling fluidization technology, two different air inlet distributions have been applied to the bed: even or homogeneous and uneven fluidization. In the same way, spout-fluid and spouted present the nuance of the cylindrical bed with different air inlets (only central part or air distribution through the center and periphery).

The aim of this work is to highlight the necessary costs of fluidizing the same material in different fluidization technologies, quantifying in terms of electrical power the air necessary to carry out the fluidization of the particles. The material used in this work is SiC, typically used in Concentrated Solar Power applications, with a particle diameter of 0.56mm. Its characteristics, minimum fluidization (U_mf=0.24m/s) and spouting (U_ms) velocities were previously measured: depending of height and mass: U_ms=0.76 m/s (h=12cm), U_ms=0.83m/s (h=15cm), 0.95m/s (h=17cm).

The most advantageous bubbling bed air distribution is considered to achieve similar results to even fluidization but with a 26.4% reduction in pumping costs. On the other hand, the conical spouted bed presents a 52.3% reduction in pumping costs compared to the spout-fluid bed for the same material. It should be noted that the pressure drop of the mass of particles has a notable contribution to the estimated total electrical power.