Trace Elements in Coal
AUTHOR: Robert Davidson and Lee Clarke
DATE: January 1996
The latest in the series of Perspective reports for IEA Coal Research reviews recent studies on trace elements in coal.
In this new report the emphasis is on trace elements as they exist in coal. Emissions of trace elements to the atmosphere, their concentrations in the environment and their effects, are not considered in detail.
The report concentrates on eleven trace elements identified as potentially 'hazardous air pollutants' (HAPS). These elements are: beryllium, chromium, manganese, cobalt, nickel, arsenic, cadmium, antimony, mercury, and lead.
The report begins with a description of the techniques used to determine the concentrations of trace elements in coal. Many of these techniques are destructive, in that the sample analyzed has to be digested in solvents, and an additional problem is the potential for error. These problems, including sample preparation and the repeatability and reproducibility of trace element determinations, are discussed.
The report discusses, not only the determination of trace elements in coal, but also their 'modes of occurrence'. Most of the trace elements in coal are to be found in the mineral fraction, therefore the mineralogy of coal, as it affects trace elements, is described in detail.
The potential environmental effects of trace elements are obviously among the most important considerations, even if the emissions and their effects are not the principle topics of the report. However, ways of avoiding air pollution are considered: the benefits of coal cleaning are discussed.
The last main chapter looks at the way in which trace elements are 'partitioned' in coal combustion. This partitioning controls the quantities which are emitted to the atmosphere or whether the trace elements are captured in the ash.