Key effect of preparing coal water slurry from Na+/Ca2+ in wastewater: slurrying & co-combustion process

The increasing discharge of high-salinity industrial wastewater poses serious environmental and resource challenges, necessitating innovative utilization approaches. In this study, high-salt wastewater containing Na+ and Ca2+ ions was employed to prepare coal water slurry (CWS), and its slurrying behavior, stability, and co-combustion characteristics were systematically investigated. Thermogravimetric (TG-DTG) analysis was used to explore combustion performance and reaction kinetics, revealing that elevated salt concentrations weaken slurry stability through double-layer compression but simultaneously enhance combustion reactivity. NaCl promotes combustion throughout all stages, while CaCl2 mainly acts in the middle and later stages due to its stronger polarization and catalytic effects. These findings provide valuable insights into the physicochemical mechanisms governing salt ion-coal interactions and demonstrate the feasibility of harmless and resource-efficient utilization of high-salt concentrated wastewater. The study offers a practical pathway for achieving clean coal utilization and wastewater resource recovery.