ABSTRACT
This chapter provides an overview of the behavior of trace elements through coal combustion and gasification processes, and the influence of pollution control devices on trace element emissions. The chemical and physical processes occurring during coal utilization are complex. Physical processes related to plant design, pollution control devices, turbulence, temperature profiles, and other parameters all affect the distribution of trace elements. Trace elements are introduced into the gasification process in the fuel coal, apart from a few elements introduced in additives or fluxes, or from the degradation of gasifier lining refractories. The fraction of the total ash reaching the pollution control devices depends on plant design. Coal is the main source of trace elements in coal-fired combustion or gasification systems, although some elements are introduced in sorbents, additives, or fluxes. Trace elements are partitioned into several output streams, including solid coal residues, residues from pollution control systems, waste waters, and flue gases.
