Solid–gas reactors driven by concentrated solar energy with potential application to calcium looping: A comparative review

The calcium looping process, based on the reversible calcination–carbonation reaction cycle of CaCO3-CaO, is an emerging and promising technology for thermochemical energy storage in concentrating solar power plants. In this process, concentrated solar energy is used to carry out the endothermic solar-driven calcination of CaCO3 with formation of CaO and CO2 as products in a solid–gas reactor. In this review, a number of experimental studies of solid–gas reactors driven by concentrated solar energy are discussed, with a particular focus on solar reactors for calcination of CaCO3 or with that potential application. The solid–gas reactors for solar-driven calcination of CaCO3 reported in the literature achieved a total efficiency of 16.6%–88% for a mass flow rate up to 25 kg h−1 and a power up to 55 kW. Also, a detailed comparison of the different types of solid–gas reactors driven by concentrated solar energy is provided by outlining their advantages and disadvantages according to several relevant criteria. This review is intended to be a valuable tool for the selection of a reactor configuration for future studies related to solar-driven calcination of CaCO3.