Chapter 4 - Definition of modes of occurrence of elements in coal

Abstract

The modes of occurrence of the elements in coal describe the way that they are chemically bound and physically distributed. The modes of occurrence of some elements are useful guides to the origin of some of the inorganic components of coal (i.e. derived from distal ash falls, weathering and erosion of rocks in sediment-source regions, hydrothermal solutions, seawater, and groundwater). It is the modes of occurrence of the elements that allows us to anticipate how the element will behave on coal cleaning, combustion, liquefaction, and gasification. The modes of occurrence also provides insights into the potential for causing technological problems, environmental issues, and human health impacts and allows us to determine if and how the elements can be considered for economic by-product recovery. This chapter divides the types of modes of occurrence of elements in coal into inorganic/mineral, intimate organic, and organic associations. Most elements in coal have quite varied and complex modes of occurrence, reflecting the multiple sources and complex geologic history of the coal but established geochemical principles apply.