Distribution of rare earth and selected trace elements in combustion products of Yerkovetskoe brown coal deposit (Amur Region, Russia)

摘要

Major, trace, rare-earth elements, and noble metal have been analyzed from the brown coal of the Amur region (Russian Federation) and coal combustion products to understand the provenance and depositional environment. It was discussed that weathering crusts of ore deposits and host rocks located in the mountain-folded frame of the Zeya-Bureya coal-bearing sedimentary basin were the main source of mineral substance and chemical elements in brown coals. The distribution of minerals and elements inside the forming coal seams was influenced by the type of vegetation incorporated into coal-forming peat mires bog by catastrophic floods along the existed hydraulic network, the physicochemical parameters of plant debris transformation during their conversion to coal, as well as the sorption properties of inclusions and interlayer of bitumen and humic acids in coal beds. An experimental technological complex was created to study the microelements transfer process in the dust-gas stream and the distribution of rare earth and trace elements separately in varieties of coal combustion products (slag, fly ash, dust-like part of the dust-gas flow, and technogenic cleaning water). The resulting combustion products of coal have been studied by inductively coupled plasma (ICP)-spectrometry methods (ICP-mass spectrometry and ICP-atomic emission spectroscopy). Sample preparation technique for analysis was improved to determine the elemental composition. It was established that more than 60% of trace and rare earth elements were concentrated in ash and sludge. Data on these elements' concentration in the wash water sediment demonstrated a sufficiently high efficiency of the dust-gas flow cleaning. The use of a wet scrubber, of course, solves the problem of collecting the dust and gas flow cleaning from harmful and toxic elements of coal smoke, which should be a part of the technological chain of a coal combustion process in industrial boilers. Rare earth elements, scandium, and yttrium are considered economically valuable components in the coal combustion products of the Yerkovetskoe brown coal deposit in the Amur Region.