Production of clean coal with low-ash from hard coals and research on recovery of rare earth elements from coal tailings

In today's world, the demand of the societies for energy is increasing with the developing technology. In parallel with this situation, the existing reserves of energy raw materials are decreasing rapidly. Coal has been one of the most important fossil fuels meeting the world`s commercial energy demand for decades. Considering the limited share of renewable energy sources in total energy production of world, strategic planning of clean energy production from domestic coal sources is of great importance for the developing countries such as Turkey from a strategic point of view. Within the scope of this doctoral thesis, studies were carried out on two different subjects related to each other. In the first stage, the possibilities of producing a low ash, low sulfur and high calorie clean coal from Zonguldak hard coal were investigated. For the production of clean coal, autoclave leaching tests have been carried out in addition to the flotation and atmospheric leaching processes. A clean coal product containing 1.04 percent ash, 0.37 percent sulfur and having 8390 kcal/kg higher calorific value on dry basis with a weight recovery of 38.26 percent was produced by the application of these methods in combination. The presence of rare earth elements in clay minerals accompanying coal in coal deposits has been identified in many studies conducted by different researchers. The recovery of these strategically important elements constitutes the second part of the doctoral thesis study. In this part of the research, studies have been carried out for the recovery of some rare earth elements from synthetically prepared rare earth element containing clay minerals. In the tests for the recovery of rare earth elements, four different clay samples were studied, and rare earth elements were obtained in yields reaching 80 percent using different solvents.