Characterizing High-Quality Illinois Limestone

Quarry mining high-calcium limestoneIllinois State Geological Survey geologist Zak Lasemi submitted the final technical report to the Illinois Clean Coal Institute for a project dealing with the characterization of high-calcium limestone for flue-gas desulfurization near Illinois coal-fired power plants. Illinois is experiencing increased demand for high-calcium limestone for flue-gas desulfurization. High-calcium (CaCO3) limestone is not widely present in Illinois, however, and most limestone quarries consist of multiple layers or ledges whose CaCO3 content and quality vary significantly. The project study compiled and updated geologic maps showing the location of high-calcium limestone resources. The study also conducted a layer-by-layer examination of selected limestone quarries in order to identify and characterize the high-calcium limestone zones, especially those with CaCO3 contents of 95% or more. More than 600 samples were analyzed for mineralogical and chemical content. The results show that high-purity limestone (>95% CaCO3) in Illinois is mostly confined to rocks that are older than the Pennsylvanian System and are at or near the surface in western and southern Illinois, especially near the Mississippi and Ohio Rivers. Very little high-calcium limestone is found in the northern part of the state where the dolomite of the Ordovician and Silurian Systems predominate. This study provides a valuable database for the location and properties of high-calcium Illinois limestone needed for flue-gas desulfurization.