Chapter 10 - Critical elements in coal

Abstract

World economies largely depend on critical elements, including Ge, Ga, U, V, Se, rare earth elements and Y, Sc, Y, Nb, Au, Ag, platinum group elements, and Re, as well as some base metals, such as Al and Mg. These metals are becoming scarce and expensive as their resources in conventional ores are exhausted and as the demand for these elements has grown rapidly due to their wide applications. In addition, supplies of these metals are controlled by a limited number of sources. These factors have initiated a global treasure hunt by way of exploration for new sources of these critical elements (particularly for REE). One promising source of many of these elements is coal and/or coal combustion products. Indeed, the concentrations of these elements in some coals and CCPs are comparable to, or even higher than, those found in conventional ores. In this chapter, several selected critical elements including U, Ge, REY, Ga, and Al, are overall described as these elements have been widely studied in recent years. Followed the detailed description of REY including their classification, economic evaluation, origins and anomalies; and case studies of U, Ge, Ga-Li-Al-REY, and REY in coal, showing how these critical elements occurs in these coals and why they were enriched.