Dolomites are not used as SO2 sorbents in fluid combustion technology. The literature data show fundamental discrepancies in the possibility of such use. They mainly concern the role of magnesium in the sorption process of SO2 and the durability of desulfurization products under high-temperature conditions. The article demonstrates that MgO is actively involved in the SO2 binding under fluidized furnace conditions. The resulting products of sulfation contain magnesium in their compositions, and their thermal transformations begin only after the temperature exceeds 1100 °C. It has been shown that dolomites are a potential raw material for the production of SO2 sorbents for fluid combustion technology, and their use is justified due to the higher desulfurization efficiency. Parameters of dolomite descriptions were given, by which it will be possible to predict the effects of flue gas desulfurization before the dolomites’ use in industrial conditions. It has been shown that there are opportunities to expand the domestic raw-material base for the production of SO2 sorbents, based on both dolomite resources present in deposits and dolomite waste accumulated in dumps, as well as generated during the current exploitation and processing of dolomites.
Disposal sites for both industrial and communal waste are hazardous for the natural environment due to the accumulated materials and their chemical, physical and biological transformations. The products of these processes migrating at a significant distance contaminate mainly underground waters, surface waters and soils. The spreading of the pollutants may be prevented by horizons of clay rocks that form natural geological barriers. The clay rocks of properly selected parameters may be used in the environmental engineering for constructing artificial water-sealing layers. The mineral, chemical, physico-chemical and physico-mechanical properties of the beidellite clays occurring within the lignite deposit in Bełchatów were studied to find out whether they meet the criteria of waterproofing engineering contained in the Polish recommendations and instructions. The results indicate that the beidellite clays of Bełchatów are rocks suitable for this kind of environmental engineering and may be used in constructing the barriers preventing the migration of effluents from landfills.
Jurassic limestones of the Kleszczów Graben are among the most important accompanying raw materials in the Bełchatów lignite deposit. In recent years, there has been a need to recognize their suitability as SO2 sorbents for use in the energy industry. The limestones are characterized by high lithological variability. They show both high hardness and compactness, and are weakly concise or even silty. At the top parts, they are subjected to karst processes. The lower parts are affected by secondary mineralization processes, among which the silicification process is most advanced. The effects of other transformation processes, such as compaction, cementation, dissolution and recrystallization of calcite are also visible. These processes contributed to a significant diversification of the mineral and chemical composition of limestone, and differentiation of physico-chemical and physical-mechanical parameters responsible for assessing the suitability for their commercial use as a raw material for the production of SO2 sorbents. Other problems associated with documenting the limestones in the Bełchatów deposit are related to their lesser importance compared to the main mineral. Its degree of exploration is low, characterized by a lower density of exploratory boreholes and significantly longer average lengths of samples collected from drill cores. At the present stage of the accompanying mineral exploration, only a preliminary estimation of limestone resources as potential SO2 sorbents is possible. The precise estimation will be possible after constructing a 3D model of criterion parameters and developing an extraction scenario.
Limestones of the Jurassic age are one of the most important minerals accompanying the Bełchatówlignite deposits. They are part of the Bełchatów and Szczerców rock subsoil complex and form natural hillsides of exploitation fields, which are gradually being exposed due to the progressive exploitation of coal. So far in Bełchatów Lignite Mine nearly 2 million tonnes of limestones have been extracted, which were used in the form of highway aggregate. For the extraction (mineral recovery) approx. 2 million tonnes remained in the Bełchatów field and from 20 to nearly 70 million tonnes in the Szczerców field. The limestones occurring in the deposit Bełchatów are differential qualitatively. Those situated in direct contact with Neogene deposits are characterized by strong karstification (karst formation), and even occur in the form of detrital minerals. Furthermore, they are covered by processes of secondary mineralization. These processes caused significant diversity of phase and chemical composition, and thereby have contributed to reducing the CaCO3 content. Despite this, limestones from the Mesozoic-Neogene contact zone possess excellent sorption properties in respect of SO2 in conditions of fluidised furnaces. These properties are determined firstly by their structural-textural nature, and above all with the presence of calcite sparite crystals in microcrystalline groundmass, of micropores, tectonic discontinuities, fracturings and compaction slits. With their presence, both decarbonatization and sorption processes proceed effectively. The CO2 particles are quickly removed from the structures of calcite crystals, and SO2 is able to penetrate into the interior of the sorbent grains where are absorbed on the inner surface of pores arising as a result of the decarbonatization process. These characteristic structural and textural properties of the surveyed limestones have been shaped at the diagenesis and epigenesis stage. This contributed to all chemical and mechanical compaction and cementation processes, as well as the dissolution and recrystallization processes. Despite the low CaCO3 content limestones from the Mesozoic-Neogene contact zone can be successfully used in the form of sorbents to reduce SO2 emissions in conditions of fluidised furnaces.
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