Structural studies of Barapukuria coal by infrared spectroscopy

Abstract

Samples colleetedfrom different depth of bore-hole GDH-38 and GDH-39 of Barapukuria coal mine were characterized physically as well as structurally. The physical characterization was done by proximate analysis according to ASTM standards (D3172). The coals were found to have low moisture, low ash and high volatile matter and high calorific values on the basis of which the coals were ranked as high volatile bituminous type. The average moisture and ash content of the coals of bore hole GDH-38 were aboul 2.69 wi % and 5.19 wi % respectively with an average volatile matter content of 35 % and Fued carbon content 0/61 % on dry ashfree basis The average moisture and ash content of the coals of bore hole GDH-39 were about 3.48 wI % and 6. 07 wI % respectively with an average volatile matter content of 34.5 % and Fixed carbon content of 64 % on dry ash free basis. The calorific values of the coals of these two bore-hole were about 15042 and 15044 Btu/lb respectively Structural characterization was accomplished using infrared (1R) spectroscopy, X-ray diffraction (XRD) analysis and particle induced X-ray emission (FIXE) spectroscopy. KEr technique was applied and a double infrared spectrophotometer was used to take the IR spectrum of the coal samples. Different organic and inorganic constituents were identified. The coals show considerable absorption in the aromatic ring vibration region at 1600 cm-I and in the aromatic wag region between 900 and 700 em"l, which signifies that the coals contain • considerable portion of aromatic compound. Large absorption at 1130 cm-l suggests that the coals are siliceous in nature. From XRD, d-spdcing for planes and stack height parameter and layer diameter for crystallite region were calculated and different mineral such as kaolinite, pyrite etc were identified. IR and XRD analysis were performed on ,'-c--oa~lsi'carbonize, d-1' at different temperature upto 900 (JCand structural changes were observed. An increase in absorption in 1600 cm-I band and in the aromatic wag region between 900 to 700 em'] was observed, up to 500 QC indicating an increase in aromatic condensation. At higher temperatures the coals were found to become opaque to JR so that no further information could be gained at temperatures above 500 Qc. The X.ray diffraction analysis was helpful in this case. The coals exhibited an increase of stack height parameter and layer diameter during carbonization indicating clearly condensation of aromatic ring, which made the coals opaque to JR. PIXE analysis of the coals samples of bore-holes GDH.38 and GDH.39 of Barapukuria and of bore.holes GDH.45 and GDH.46 of Khalashpir mine were performed using 2.5 MeV proton beamfrom Van de Graaff accelerator. 19 elements including enviromilentally hazardous arsenic, bromine, copper, lead, selenium and economically important gallium and germanium along with major elements like iron, calcium, potassium manganese etc were detected and analyzed for their concentration. The concentration of these trace elements in Barapukuria and Khakaspir coals were compared with their respective values in some CanadIan coals and in earth's crust. The results were similar with a few exceptions.