05/02399 Exploring the possibilities of using Brazilian subbituminous coals for blast furnace pulverized fuel injection

Abstract

The basic coal quality parameters, coal petrology, mineralogy and geochemistry were investigated for coal seams 2, 3 and 4 (Permian Shanxi Formation) and 11, 12, 13 and 15 (Carboniferous Taiyuan Formation) of the Xinwen and Feicheng coal fields in the West Shandong mining district, East China. Rank parameters indicate a high volatile C to B bituminous rank for the Shandong coal. Coal from the Zhaizhen and Cha Zhuang mines is characterised by high vitrinite and low–middle inertinite and liptinite contents. Inertinite contents show an increase towards the top of the stratigraphic sequence from coal seams 15, 13 and 11 to coal seams 4 and 2. This trend may be related to a stratigraphic trend characterised by the evolution of relatively more reducing conditions of the synsedimentary coal forming environment in the early Taiyuan coals (marine-influenced lower delta plain) to more oxidising paleoenvironments of the Upper Shanxi coal seams (upper delta plain). Major mineral phases present in the Shandong coal are quartz, kaolinite, pyrite and calcite. Traces of other primary minerals (dolomite, ankerite, illite, opal, feldspars and marcasite) and weathering products (gypsum, melanterite and hematite) can be found in several coal seams. The Lower Permian coal seams (two to four) have a lower mineral content (8–14% ash db) than the Upper Carboniferous coal seams (15–37% ash db), owing to the lower proportions of quartz and sulphide mineral. The occurrence and distribution of the different minerals in the Shandong coal indicates a paragenetic sequence characterised by an early syngenetic stage (detrital minerals, framboidal, euhedral and massive cell-filling pyrite, ankerite, neomorphic quartz and kaolinite), middle and late syngenetic stages (radial and fibrous marcasite aggregates, massive pyrite) and an epigenetic stage (carbonates and sulphides as cleat filling). A clear differentiation exists between the Shanxi and the Taiyuan coal seams, based on the higher sulphide contents of the Taiyuan coal (3.3 to 6.2% S db) compared with the Shanxi coal (0.4 to 0.8% S db). This differentiation is related to marine influence on the depositional environment of coal seams 11 to 15, which has been reported by earlier studies. Vertical variations of the abundance of major and trace elements are discussed on the basis of this differentiation. An epigenetic external enrichment of Ge, Mo and U at the top of most of the coal seams is observed, and major and trace element affinities are deduced for the West Shandong coal.