Pilot-scale demonstration of Ca–Cu looping for CO₂ capture from blast furnace gas

To achieve deep decarbonization in steel-making, scalable CO 2 capture technologies are required for blast furnace gas (BFG). This work reports key experimental results obtained in a TRL7 pilot plant for individual stages of a novel Ca Cu solid looping process for simultaneous H₂-rich gas production and CO₂ capture from real BFG. A packed-bed reactor (5 m height, 0.5 m inner diameter) was operated at ArcelorMittal's Gas Lab in Asturias (Spain) using 620 kg of commercial Ca- and Cu-based solids and processing up to 140 Nm 3 /h of steel mill off-gases. During the Calcium-Assisted Sorption-Enhanced reaction of BFG (CASOH), more than 90% of CO 2 removal was achieved, with nearly complete CO conversion to H 2 through reaction with H 2 O, producing an H₂/N₂ stream with up to 35% H₂ (dry basis). The oxidation and reduction stages confirmed the fast redox kinetics of the Cu/CuO pair, enabling nearly complete gas conversion during the pre-breakthrough periods. An advanced regeneration strategy of CaO, based on CO₂ partial pressure swing, was also successfully demonstrated. This approach aims to exploit the heat generated during the exothermic stages of the CASOH process, retained within the solids bed, to drive the decomposition of CaCO₃, potentially producing a CO₂ stream of very high purity. The pilot results suggest that the CASOH process could represent a technically feasible and scalable pathway for the decarbonization of BF-based steelmaking. • The TRL7 CASOH pilot captures CO₂ from real blast furnace gas with high efficiency. • The 620 kg packed bed achieves >90% CO₂ capture and near-complete CO conversion. • CASOH upgrades BFG into H₂-rich gas streams reaching 35 vol% H₂. • Fast and stable Cu/CuO redox kinetics demonstrated under cyclic operation • CO₂ partial-pressure-swing regeneration enables high-purity CO₂ production.