Carbonation tests in a kW-scale entrained flow reactor for thermochemical energy storage using the calcium looping-based system

Deploying reliable and sustainable large-scale energy storage is a significant challenge for the widespread adoption of renewable energy sources. Thermal energy storage solutions can provide scalable solutions for renewable power and industrial processes. The calcium looping-based energy storage system stands out for its high energy density, low cost, non-toxicity, and wide availability of limestone as a precursor material. The thermochemical energy storage cyclic process occurs through the calcination of calcium carbonate and its subsequent recovery through carbonation of calcium oxide. This work presents the development and tests of a novel entrained flow carbonator developed during the SOCRATCES EU project. The results show for the first time a successful CaO carbonation reaction in kW-scale equipment under energy storage conditions. The carbonation reaction occurs in an entrained flow reactor in few seconds at the temperature and pressure conditions required for the Calcium-looping-based energy storage system (700–800 °C). It demonstrates the feasibility of the entrained flow reactor concept for carbonation and its potential for MW-scale solar plants. • First kW-scale pilot plant for calcium looping under energy storage conditions • An entrained-flow carbonator with stable solids feed was integrated into a TCES plant • Over 60 % carbonation conversion reached in seconds at temperatures above 750 °C • Particle sizes 15–25 μm improved flow and reaction performance over finer materials • kW-scale tests confirmed TRL increase from 4 to 5 under real TCES-CaL conditions