CO2 abatement from the iron and steel industry using a combined Ca–Fe chemical loop

We report an integrated CO2 capture process to manufacture iron and steel with low CO2 emissions from steel-making plants over a CaO-based, Fe-functionalized CO2 sorbent. This new process relies on a combined Ca–Fe chemical loop, where the exothermic oxidation of FeO provides the heat (or fractions of it) required to drive the endothermic decomposition of CaCO3. A key advantage of coupling a FeO/Fe2O3 redox cycle and a CaO/CaCO3 CO2 capture cycle within the as-prepared materials is that the heat could be transferred from FeO to CaCO3 directly at a molecular level. All materials synthesized require an appreciably reduced net heat, i.e. a decrease of 26–43%, for CaCO3 decomposition during the combined Ca–Fe looping when compared with conventional calcium looping. Importantly, materials CaFe-CA1EG1-pH1, CaFe-CA1EG1-pH2, and CaFe-CA1EG1-pH3 exhibit a fairly stable cyclic CO2 uptake of ∼0.16gCO2gsorbent−1 throughout 10 realistic combined Ca–Fe looping cycles. The medium capacity but excellent stability for CO2 capture of the CO2 sorbents makes them a promising alternative of naturally-derived, CaO-based materials, especially for the combined Ca–Fe chemical loop proposed. Using steel slag as feedstock, the material developed is very promising for CO2 abatement from the iron and steel industry accompanied by the recycling of CaO and Fe2O3 components in spent sorbents and recovery of energy from process gases.