Genetic–industrial classification of brown coals in Serbia

Abstract

Abstract The petrologic, chemical and technological features of low-rank coals from nineteen of the most important basins in Serbia have been studied as part of the research project of genetic–industrial classification of low-rank coals of Serbia. Most of these features have been included as parameters of the codification system for low-rank coals. The paper discusses the main genetic, technological and supplementary parameters of the Serbian brown coals such as rank, petrographic composition, gelification degree, total moisture, ash content, sulphur content, calorific value, tar yield, the chemical composition and the thermotechnical properties of ash. The rank of brown coals from Serbia has been defined on the basis of the following parameters: random reflectance of huminite/vitrinite (Rr = 0.26–0.50%), total moisture (War = 13.18–49.11%), gross calorific value (Qdaf = 22.3–29.2 MJ/kg, dry, ash-free basis), net calorific value (Qdaf = 21.2–28.1 MJ/kg, dry, ash-free basis). The results from the maceral analysis confirm that the humic coals, in general, are characterized by high huminite content (76.0–97.9 vol.%, mineral matter free), low inertinite amount (0.7–6.3 vol.%, mineral matter free), and a variable amount of liptinite (0.8–15.5 vol.%, mineral matter free). It is possible to define three groups of Serbian brown coals on the basis of the primary, or genetic parameters, technological, or chemical parameters, and supplementary parameters: soft (Low-Rank C; [Economic Commission for Europe, Committee on Sustainable Energy– United Nations (ECE-UN), 1998. International Classification of in-Seam Coals. Energy 19, 41 pp.; Economic Commission for Europe, Committee on Sustainable Energy– United Nations (ECE-UN), 1999. International Codification System for Low-Rank Coals. Energy 9, 19 pp.; Economic Commission for Europe, Committee on Sustainable Energy– United Nations (ECE-UN), 2000. International Classification for Low-Rank Coals. Energy 12, 21 pp.]), dull (Low-Rank B) and bright brown coals (Low-Rank A). The soft brown coals of Serbia contain a high percentage of total moisture (43–56%), and ash (30–43%, dry basis). These coals have a high volatile matter content (55–75%, dry, ash-free basis), and a relatively low carbon content (54–65%, dry, ash-free basis). The gross calorific value ranges between 22 and 26 MJ/kg (dry, ash-free basis), the net calorific value is between 20 MJ/kg and 25 MJ/kg (dry, ash-free basis), and the huminite/vitrinite reflectance ranges between 0.26%Rr and 0.30%Rr. The dull brown coals of Serbia have 17–47% of total moisture, 18–35% of ash content (dry basis), 50–60% of volatile matter content (dry, ash-free basis), 63–67% of carbon content (dry, ash-free basis), gross calorific value of 26–28 MJ/kg (dry, ash-free basis), net calorific value 24–27 MJ/kg (dry, ash-free basis), and huminite/vitrinite reflectance 0.31–0.40%Rr. Bright brown coals have 13–28% of total moisture, 14–27% of ash (dry basis), 50–60% of volatile matter content (dry, ash-free basis), 65–72% of carbon content (dry, ash-free basis), gross calorific value 26–30 MJ/kg (dry, ash-free basis), net calorific value 25–29 MJ/kg (dry, ash-free basis), and huminite/vitrinite reflectance of 0.41–0.50%Rr. This is the first comprehensive report on the genetic–industrial classification of brown coals from Serbia according to the selected parameters and on the possibility of their utilization in industry for combustion, liquefaction and briquetting.