Feasibility of thermal treatment of high sulfur coal wastes

Δημοσίευση σε επιστημονικό περιοδικόSummarization: Coal mining and processing activities in Russia result in the generation of huge quantities of wastes containing elevated concentrations of residual S (Sdt=2.1–9%), C (Cdo > 12%), heavy metals and other hazardous elements. These wastes which are usually piled or dumped without specific care close to mining sites and processing plants are subjected to adverse climatic conditions and in most cases cause severe impacts to various receptors. The worst impacts, in Russian mining and disposal areas, are due to the oxidation of the residual sulfide phases and the generation of coal mine drainage, with pH often ranging between 2.5 and 4. These acidic leachates contaminate severely soils, surface- and groundwater; therefore the risk for humans and ecosystems in these sites is considered as extremely high. The present paper examines the feasibility of thermal treatment of high sulfur coal wastes, in particular those containing elevated content of carbon, kaolin and iron, in order to reduce environmental risk at the disposal sites and produce saleable by-products. Carbon reduces substantially fuel consumption while kaolin and iron assist the formation of secondary products. Parameters studied include temperature and air excess ratios, up to 1400 °C and 1.4 respectively. Coal wastes were subjected to thermal treatment (a) as such, in order to study the removal of sulfur and the production of saleable products (sulfuric acid, various construction materials, products with high magnetic susceptibility, aluminum sulfate) and (b) after mixing with calcium carbonate in order to study the fixation of sulfur in multi-mineral phases possessing binding properties. Prior to implementation of laboratory experiments in order to assess the potential of thermal treatment, thermodynamic calculations were performed to determine optimum operating parameters and possible phase transformations.Παρουσιάστηκε στο: Minerals Engineerin

Environmental and economic potential of thermal treatment of high-sulfur coal wastes

Summarization: Coal mining and processing activities in Russia have resulted in the accumulation of large volumes of coal wastes containing high residual content of S and C. If these wastes are disposed improperly in the environment they are considered as active sources of coal mine drainage generation which severely contaminates soils, surface-and groundwater and endangers the ecosystems of the area. Thermal processing or stabilization of these wastes enables, apart from minimizing environmental impacts in regions with intensive coal mining activities, the recovery of useful components increasing thus the overall economics of the process and substantially reducing the required rehabilitation costs. The present paper examines the environmental and economic potential of thermal treatment of coal wastes. Parameters studied include temperature and excess air ratios, ranging between 600-800 o C and 0.6-1.2 respectively. Wastes were subjected to thermal treatment as such in order to study the removal of sulfur and the production of saleable products (sulfuric acid and various construction materials) or mixed with calcium carbonate in order to study the fixation of sulfur. Prior to experimental studies thermodynamic calculations were performed in order to select the optimum operating parameters and predict phase transformations.Παρουσιάστηκε στο: SWEMP 02 Conference Proceeding