98/01792 Bin discharge characteristics of crushed coal. An experimental study : Bhattacharya, S. et al. Braunkohle, 1997, 49, (6), 573–576

Abstract

High-rank organic matter (OM) (from Ess coal stage to meta-anthracite) of different concentrations has been studied by means of coal petrography and coal chemistry. Sixty polished surfaces (blocks and from kerogen concentrates), as well as 30 samples from mines in the southwestern Donets Basin, where the Middle Carboniferous (Mississippian) high-rank coals occur, were analyzed. Major emphasis has been laid on establishing the optical features and petrographic composition of coals and dispersed organic matter (MOD) in different facies, from terrigenous alluvial to marine limestones. The influence of tectonic structures and mineralization on the properties of coal matter were also taken into account.A general evolutionary trend of OM of different concentration is observed on the basis of changes in the optical features and chemical properties. At high ranks, there is a distinct change in vitrinite reflectance and anisotropy at R0max of about 2% and carbon content of 90% (Cdaf). The next, less distinct jump in coalification takes place during the transition from the anthracite to metaanthracite rank at R0max Vt = 6% and Cdaf = 96%. In most cases, vitrinite reflectance and anisotropy in coals are higher than those of MOD from nearby locations. The lowest values of R0max and anisotropy are recorded in OM of limestones.At all stages in the metamorphic series there are differences in the elemental composition and real density values between coals and MOD. MOD displays features of elevated primary oxidation as compared to coals.It would be reasonable to subdivide anthracites proceeding on the basis of the elemental composition of coals and MOD, using atomic percent values.Despite the convergence of the optical features of various macerals in the course of coalification, and owing to irregular changes in the maximum and minimum R0 values at high metamorphic grades, one can draw a reliable distinction between fragmentary homogeneous and structural plant remains, among them spores and algae. No appreciable changes are recorded in the size of liptinite macerals in anthracites as compared to less metamorphosed coals.The alteration products of higher and lower plants are slightly different in their chemical characteristics at anthracitic rank. Sapropelic coals have a lower amount of hydrogen as compared with humic coals.The presence of pyrite in coals results in local (microscopic) changes in R0max and R0min of vitrinite and a decrease of its bireflectance value. In tectonically dislocated areas, there is no appreciable increase in OM reflectance. However, in these areas anisotropy quite frequently does increase.The data obtained can be of great significance in working out the classification of coals in the more advanced stages of the coalification series, defining the nature of organic inclusions in host rocks, and in accomplishing studies on black shale metal-bearing complexes, which contain carbonaceous matter of anthracitic and meta-anthracitic rank.