Abstract
The chemical composition of coal mineral matter, and particularly the content of major elements (Al, Si, Fe, Ca, K, Na, Mg), plays an important role in the processing and use of bituminous coals. Mineral matter is the ballast, reducing the calorific value of the fuel. The aim of the study was to analyze the concentrations of main elements of coking coal mineral matter and products of its cleaning in heavy media, jiggers and flotation machines. Analysis of elements was performed through the technique of the atomic absorption spectrometry AAS. The results of main elements concentrations of coal mineral matter and its cleaning products are discussed in relation to each operation of mechanical treatment. As a result of the cleaning process in heavy media, the content of mineral substances decreased seven times, mainly due to the removal of components such as silicon, aluminum and iron from coal. Similar results were obtained in the case of cleaning in jiggers, leading to a significant reduction of the contents of silicates and aluminosilicates. In both cases, there was an increase in the content of sodium. Despite the significant reduction of the contents of alkali metals’ compounds, their content in concentrates as converted to oxides is quite high (0,43–0,81% of dry coal). The lowest alkalis content is the displayed by a coal concentrate from the flotation process dewatered in a centrifuge.
Highlights
Coals, in particular bituminous coals, due to their properties are a valuable natural resource with a variety of applications in a number of industries
From the point of view of the processes during the thermochemical treatment of coal, the elemental composition of coal mineral matter plays an important role, in particular content of the so-called major elements (Al, Si, Ca, Mg, Fe, Na and K) which determine the directions of processing and properties the final products
The chemical composition of the mineral matter can constitute the basis for predicting the quality of solid product of coking, combustion and gasification of coal
Summary
In particular bituminous coals, due to their properties are a valuable natural resource with a variety of applications in a number of industries. Many compounds that occurs in the coal mineral matter (alkali, sulphur compounds, iron and magnesium) have a negative impact on the process of thermochemical processing of coal. In gasification processes alkaline compounds cause the formation of lesions in gasifiers reducing their efficiency. In the process of the pyrolysis about 40% of alkaline compounds passes to coke, being the source of the blast furnace accretions that breaking away of from the walls of the blast furnace leads to clogging of the nozzles and the blast furnace burnout. A significant part of coal mineral matter is aluminum (Al) and silicon (Si) They are basic component of silicates and aluminosilicates. Quartz and opal in 800°C transform the structure of its crystal lattice - 870°C quartz is converted to tridymite, and opal at 100°C loses water, and at high temperature it passes transformations similar to quartz
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