Enhanced CO2 capture via calcium looping with mesoporous ladle furnace stainless steel slag

Abstract

CaO-based materials have attracted considerable interest because of their potential roles in thermochemical CO₂ capture via the calcium looping (CaL) process. The steel manufacturing sector inevitably generates substantial amounts of slag as a by-product, posing environmental issues such as soil contamination if left untreated. Despite its abundance and low cost, steel slag, which contains 20–60 % CaO, has not been extensively researched for its potential in the CaL process. This study introduces ladle furnace slag (LFS) as an optimal CaO-rich material for developing mesoporous composites to improve CO₂ sequestration in the CaL process. Using an autoclave reactor/muffle furnace setup, we conducted a parametric investigation on operational variables including reaction time, temperature, pressure, and liquid-solid ratio and determined the kinetics of carbonation/calcination reaction of CaL process. Our findings reveal that the CO₂ capture performance of modified LFS surpassed that of the bare LFS, achieving a CO₂ uptake of 7.55 ± 0.01 g per g of sorbent over 20 cycles. Additionally, the modified LFS exhibited the capability to undergo a minimum of 20 regeneration cycles, reaching steady state after the 15th cycle with minimal variation of 0.01 g per g of sorbent. The enhanced stability was linked mainly due to the presence of ceramics such as Al₂O₃ and Fe₂O₃ in ratios of 1:5 and 1:6.5 respectively, with respect to CaO, achieved through acid etching. Such mineralogical transformation of the modified LFS improved its resistance towards sintering while ensuring 100 % recycling of metals in the LFS. Therefore, this study highlights the sustainable utilization of LFS as a valuable and efficient sorbent for CO₂ capture, showcasing its potential for repurposing in environmental applications.