Traditional evaluations of surfactant fluid wettability on coal dust often overlook high-salinity water environments. Thus, it is essential to systematically investigate the impact of hardness-indicating ions (Ca2+/Mg2+) in surfactant solutions on coal dust wettability. This study explores the influence mechanisms of ion type and concentration on coal–water interfacial behavior modified by various surfactants through macroscopic wettability experiments (surface tension, contact angle, spreading work, coal dust settling, viscosity, and foaming) and microscopic molecular theoretical calculations (quantum chemistry and molecular dynamics). Macroscopic results show that under optimal wettability concentrations, surface tensions of YL (anionic) and YG (cationic) series rise at different rates with increasing hardness, while viscosities exhibit U-shaped and arch-shaped trends, and foaming capacities decline stepwise. FL (nonionic) series surface tensions follow a decline-then-rise pattern, with minima of 29.1 mN/m (Ca2+) and 28.9 mN/m (Mg2+), and hardness thresholds align with YL and YG at Ca-500 and Mg-700. FL viscosity and foaming remain stable. The best hard-water tolerance and wettability are observed in 0.2% YL-1, 0.25% YG-1, 0.2% FL-1, and 0.2% FL-3, while 0.2% YL-1 and 0.25% YG-1 excel in atomization. Microscopic calculations reveal high sensitivity of YL-1 and YG-1 to Ca2+/Mg2+, whereas FL-1 and FL-3 show limited wettability changes due to ethoxy groups. The differing effects of Ca2+ and Mg2+ stem from variations in their charge-to-ionic radius ratios. These findings provide theoretical insights for optimizing dust suppressant performance.

As the largest carbon emitter in China’s manufacturing sector, the low-carbon transition of the steel industry is urgent. CO₂ capture, utilization, and storage (CCUS) technology is one of the effective measures to reduce carbon emissions in steel industry. In this paper, a comprehensive assessment model of source–sink matching-levelized cost in China’s steel industry is constructed to evaluate the potential, economy, and spatial distribution of CCUS retrofits of blast furnaces in the BF-BOF steel industry. The results show that, if no extra incentive policy is included, the levelized cost of carbon dioxide (LCOCD) of 111 steel plants with a 420.07 Mt/a CO₂ abatement potential ranges from −134.87 to 142.95 USD/t. The levelized cost of crude steel (LCOS) range of steel plants after the CCUS retrofits of blast furnaces is 341.81 to 541.41 USD/t. The incentives such as carbon market and government subsidies will all contribute to the early deployment of CCUS projects. The CCUS technology could be prioritized for deployment in North China, Northwest China, and East China’s Shandong Province, but more powerful incentives are still needed for current large-scale deployment. The research results can provide references for the early deployment and policy formulation of CCUS in China’s steel industry.