CONTROL OF FLUORINE IN METALLURGICAL FUEL

Abstract

Metallurgical fuel, including various types of mineral fuels: coke, hard coal, brown coal, peat, combustible shales and products of their technological conversion – needs environmental control of their use safety. When burning metallurgical fuel, harmful substances fall into the environment such as chlorine, fluorine, sulfur, arsenic, which worsen the environmental situation. Technical regulations on the safety of coal products contain requirements to limit the content of harmful impurities and their maximum permissible concentrations. Due to the wide spread of fluorine in natural and technological objects and the high toxicity of its compounds, the control of fluorine content is an urgent problem in the industrial use of metallurgical fuel. Physical methods for the determination of fluorine in solid fuel based on excitation of different spectra of the studies allow to identify it without decomposition directly in the source solid material, however, they have several limitations (sensitivity, accuracy of definition, complexity of hardware design). In other methods, mainly in ionchromatography and ionometry, samples are decomposed and fluorine is transferred into the solution. High temperature processes: pyrohydrolysis and combustion melting are usually used for decomposition. The aim of this work was to create a selective method for ionometric determination of fluorine with a fluoride-selective electrode. The study objects were samples of coal: brown, gas, semicoke, coke nut. Effective decomposition of the samples by two-stage high-temperature melting with KNaCO3 is proposed. Hydrolysis coprecipitation of accompanying interfering cations with chloride iron (II) was carried out for fluorine discharge in the solution in the form of free fluoride. The procedure of decomposition and ionometric determination of fluorine is described. The estimation of trueness and reproducibility of the developed technique by the method of sample variation was carried out. Fluorine content in the studied samples did not exceed the limit- tolerance values for commercial samples of coal products, which indicates the environmental safety of the samples in their subsequent energy application. The developed method is promising for the control of fluorine impurity in metallurgical fuel and is characterized by selectivity and simple carrying out.