Enhancement of a Closed-loop Recycling by Converting Rejected Coal Fly Ash into Coagulants for Desulfurization Wastewater Treatment in a Coal-Fired Power Plant

Environmental policies promoting resource recycling have been implemented worldwide to achieve goals such as carbon neutrality and reducing greenhouse gas emissions. The Republic of Korea has set targets to reduce waste and increase recycling rates to 70% by 2030. Rapid advancement of artificial intelligence has led to higher energy demand, raising concerns over supply, security, and management. Despite the operation of renewable energy facilities, reliance on coal-based energy remains high, resulting in continuous coal ash generation. Most coal ash is recycled into construction materials, including concrete, while a significant portion, particularly rejected coal fly ash a byproduct is almost entirely landfilled. This has hindered improvements in recycling rates due to technological limitations. To address this, advanced recycling methods for coal ash were explored, focusing on its potential application as a coagulant, an underexplored topic. Comprehensive evaluations, including settling velocity, environmental assessment, life cycle assessment, and economic feasibility, were conducted. The results showed that the settling velocity of the rejected coal fly ash-based coagulant was more than twice that of conventional products. Regulated substances were within legal limits, although several unregulated substances were detected. Life cycle assessment indicated reductions of up to 89% in carbon emissions, energy consumption, and resource use, while economic analysis revealed cost savings of approximately 41% compared with conventional products. These findings demonstrate that rejected coal fly ash-based coagulant can serve as an effective and environmentally sound alternative, expected to enhance coal ash recycling rates and demonstrate positive results in evaluating recycling potential. Developed a novel recycling method converting coal rejected coal fly ash into a wastewater coagulant. The recycled coagulant achieved over twice the settling velocity of conventional products. Life cycle assessment showed up to 89% reduction in carbon, energy, and resource use. Economic analysis indicated about 41% lower cost compared with conventional treatment. The approach enhances coal ash recycling and promotes circular resource utilization.