Directly Irradiated Fluidized Bed Reactor for Thermochemical Energy Storage and CO2/H20 Splitting

This work deals with the development of a directly irradiated lab-scale fluidized bed reactor targeted at maximizing the collection of solar energy, withstanding the high-concentrated flux typical of high-temperature CSP applications (> 1 MW/m2) and ensuring a uniform temperature distribution of the reactive material. The reactor is made of two concentric circular columns: the internal one (OD=12 mm, ID=10 mm, length=80 mm) is referred as riser, the external one (OD=21 mm, ID=16 mm, length=70 mm) as annulus. The upper part of the annulus column is connected to a conical section (internal angle=30°, height=120 mm), which represents the freeboard of the reactor and hosts, at its extremity, a transparent quartz window to let the solar radiation enter keeping seal-tight operation of the reactor. During the reactor operation, a gas stream is fed into the internal column to induce the rise of a dense particle suspension, typically under fast fluidization conditions. At the outlet of the riser, the dense particle suspension directly interacts with the solar concentrated radiation (simulated by mean of a short-arc Xe lamp) and increase its temperature. In the freeboard zone, due to the cross-section increase, the gas velocity is progressively reduced, and the solid particles fall down on the conical section and descend along it to eventually convey into the annulus column. Here, the particles move by gravity towards the bottom, where they re-enter the riser by mean of four small holes drilled in the riser column. During their motion along the annulus section, the particles transfer their heat to the riser column, thus preheating the rising dense suspension prior to its interaction with the concentrated solar radiation.