Partitioning behavior during coal combustion of potentially deleterious trace elements in Ge-rich coals from Wulantuga coal mine, Inner Mongolia, China

Abstract

Partitioning behavior of 17 deleterious trace elements in Ge-rich coals during coal combustion was studied in a bench-scale combustion apparatus in a laboratory and in full-scale combustion in a coal-fired power plant. Methods used in this study include spectrophotometry, tube furnace combustion, inductively coupled plasma mass spectrometry (ICP-MS), and statistical evaluation. A comparison of the results obtained at these two scales and of the factors affecting their volatilization behavior during combustion are discussed. These seventeen trace elements tend to be volatilized more completely during combustion in coal-fired power plant than in a laboratory-scale combustion environment due to the differences in operating conditions. The average proportions of elements going into fly ash from feed coals during combustion are positively correlated with the trace element volatilities. Volatilization behavior of trace elements in laboratory-scale combustion involves three stages: initial release (<500 ℃), relative stability (500–1,000 ℃), and secondary release or stability (>1,000 ℃). The seventeen trace elements can be classified into four groups according to their behavior during the above-mentioned stages. Factors affecting behavior of elements in combustion, such as combustion conditions, modes of occurrence, concentrations, and geochemical affinities, are discussed. A new insight into the behavior of potentially deleterious trace elements during combustion is given, which provides further guidance to controlling their emissions.