Transient Model for Behavior of Mercury in Portland Cement Kilns

The U.S. Environmental Protection Agency has proposed to regulate emissions of air mercury from Portland cement kilns. Understanding the behavior of mercury within cement kilns will help operators of Portland cement kilns to devise methods for accurate measurement of mercury emissions and for reducing mercury emissions when regulations are imposed. A transient model for mercury behavior was developed and benchmarked with a comprehensive data set on the dynamic behavior of mercury in a Portland cement kiln reported by the German Research Institute of the Cement Industry. The model was able to reproduce key features of the transient behavior, including spikes in the exhaust gas concentration during the period when the plant switched from the raw mill on-line to the raw mill off-line; the high concentration of mercury in the electrostatic precipitator (ESP) dust; and the weekly transients resulting from operation over weekends with the raw mill on-line.