| dc.description.abstract | This study delves into the mass flow and balance of mercury in a cement plant, and investigates the emission characteristics of mercury from flue gas. Additionally, the causes of high mercury concentration in solid sample due to the implementation of circular economy policy are studied. In short, the study investigates mercury flows through out the cement plant, particularly as the plant receives fly ash with unstable mercury concentrations as recycled material. The research reveals that the primary mercury input in the cement plant investigated is iron slag (40.9%), followed by limestone (23.0%) and silica sand (13.4%). The contributions of coal fly ash (8.84%) and washed fly ash (5.67%) are also significant. The data on the mercury flow rate from raw material and recycled material indicate that mercury content of recycled material (0.2667 mg/kg) is much higher than that of raw material (0.0652 mg/kg). The study shows that the use of recycled materials, including iron slag, coal ash, and washed fly ash, has altered the structure of mercury input in this cement plant. This study also demonstrates that intermediate products of the cement production process have a strong ability to enrich mercury, with the concentration of mercury in the dust collected in raw mill reaches 19.7 mg/kg, followed by 14.7 mg/kg in dust collection in coal mill, and 2.05 mg/kg in raw meal. The mercury output of cement plant is mainly via flue gas, with the mercury mass flow rate of 16.34 g/hr, accounting for 98.8% of the total output, while the clinker output mercury mass flow rate is only 0.16 g/hr (1.1%) of total output. The mercury emission factor (MEF) refers to the amount of mercury emitted per unit clinker produced. Previous studies indicate that the MEF value ranges from 1.8 to 253 mg Hg/ton clinker. The MEF of the raw mill stack in this plant is 165 mg Hg/ton clinker, while the MEF from coal mill stack is 6.6 mg/ton clinker. The mass balance ratio of this study is 130%, which is within the acceptable range (70 ~ 130%). The circular economy has a significant impact on mercury emissions in the cement manufacturing process. The amount of recycled materials used in the cement industry is increasing year by year, and the mercury emission from the cement industry is also gradually increasing. Investigation of solid samples indicates that the mercury was chemisorbed in intermediate products, which were released again into the flue gas at high temperatures and emitted into the atmosphere in elemental form. Overall, this study indicates that we should carefully examine all the materials applied and enhance the performance of APCDs to reduce mercury emission. | en_US |