St. Petersburg Mining University (St. Petersburg, Russia):

Pashkevich M. A., Head of Chair, Doctor of Engineering Sciences, Professor, mpash@spmi.ru
Petrova T. A., Associate Professor, Candidate of Engineering Sciences, petrova9@yandex.ru
Sverchkov I. P., Postgraduate Student, sverchkov@spmi.ru

The results of the «Mezhdurechye» coal-preparation plant moist waste coal studies are presented with a view to determine promising lines for waste coal recycling. The low heating value, ash content, main fuel elements’ contents and cindery part contents were determined. It was revealed, that dumped waste coal contains approximately 60 % carbon. Waste coal ash content on a dry-matter basis is about 23 %. The low heating value of waste coal sample — 18.5 MJ/kg. It was established, that for waste coal in question the most efficient way of recycling is utilization as coal-water fuel at power generation plants. Waste coal burning as coal-water fuel will permit to significantly decrease emission of pollutants (in particular, nitrogen oxides) in comparison with conventional fuel-bed firing of coal, notwithstanding that nitrogen content in waste coal and in vendible coal is approximately the same. The reason for this is that in hightemperature (1400–1800 °C) coal combustion mainly thermal nitrogen oxides are formed as a result of the interaction of nitrogen and atmospheric oxygen. Contents of fuel nitrogen oxides (formed owing to presence of nitrogen compounds in coal) and prompt nitrogen oxides (formed in reaction of atmospheric nitrogen with hydrocarbons) are not so much dependent on temperature. Since coal-water fuel combustion temperature in swirling-type furnace is 900–1200 °C, mainly fuel thermal nitrogen oxides and prompt nitrogen oxides will be formed in off-gases. It is shown, that waste coal utilization as raw material for preparation of coal-water fuel will permit to decrease man-caused ecological impact on atmospheric air, soil, surface and groundwater.

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