Directly irradiated fluidized bed reactors for thermochemical processing and energy storage: Application to calcium looping

Directly irradiated fluidized bed reactors are very promising in the context of concentrated solar power applications, as they can be operated at process temperatures high enough to perform thermochemical storage reactions with high energy density. Limestone calcination-carbonation is an appealing reaction for thermochemical storage applications due to the cheapness of the raw material, and the interesting value of the reaction enthalpy at fairly high process temperatures. Moreover, limestone calcination-carbonation is intensively studied in Calcium Looping (CaL) application for post combustion CO2 capture and sequestration. In this work, the dynamics of a directly irradiated 0.1 m ID fluidized bed reactor exposed to a 12 kWel simulated solar furnace is analyzed with specific reference to temperature distribution at the surface and in the bulk of the bed. Simulation of the solar radiation was performed through an array of three short arc Xe-lamps coupled with elliptical reflectors, yielding a peak flux of nearly 3000 kW m-2 and a total power of nearly 3 kW incident on the bed surface. Moreover, the directly irradiated fluidized bed reactor has been used to perform CaL tests by alternating solar-driven limestone calcination and autothermal recarbonation of lime. CaL has been investigated with the twofold perspective of: a) accomplishing energy storage by solar-driven calcination of limestone; b) perform solar-aided CO2 capture from flue gas to be embodied in carbon capture and sequestration schemes.