• Bodhisatwa Hazra

      Articles written in Journal of Earth System Science

    • Petrographic controls on phosphorous distribution in coal seams of the Jharia basin, India

      Atul Kumar Varma Sumit Mishra Balram Tiwari Bodhisatwa Hazra Susheel Kumar Durga Charan Panigrahi Anwita Ojha

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      In recent years, the international coking coal market is experiencing an acute shortage of coal supply which has caused a fluctuation in its price. Degradation of coke, in the blast furnace, is largely controlled by its inherent mineral matter. Phosphorous occurs in all coals in minor or trace amounts and is an important parameter to coal users, particularly in steel industries. The mode of occurrence and distribution of phosphorous minerals in 17 coal samples of the Jharia coal basin were investigated through petrographic examinations, technological characterisation and phosphorous distribution. The results reveal that the dull bands are eight times more enriched in phosphorous than the bright bands. The macerals of the inertinite group and mineral matter positively correlate with the phosphorous content, whereas vitrinite macerals have an apathetic correlation. The impact of the thermal alterations is localised and diminishes away from the contact of the intrusion. In contrast, the faulting does not appear to have any effect on the phosphorous content.

    • Structural and thermal properties of vitrain lithotype in coal-inferences from TG-DTG-DSC, Rock-Eval and X-ray difraction


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      Vitrain is one of the most important lithotype for the end utilization of humic coals in relevant industries. In this work, we examine the thermal, structural and pyrolysis properties of vitrains, manually isolated from coals of three distinct thermal maturity levels (rank). The high volatile bituminous (HvbA) vitrainshowed highest moisture content and reactivity during combustion, while showing least Rock-Eval S2 $T_{max}$ and S4 $T_{peak}$. On the other hand, the low volatile (Lvb) sample showed properties exact opposite to that of the HvbA sample. Thus, the rank of the vitrains was observed to directly control their behaviour.Owing to their inherently lower ash content, all the vitrains during thermogravimetric analysis developed smooth thermograms, indicating easy burning. Interlayer spacing ($d_{002}$), obtained from XRD displayed astrong decrease with increasing coal rank, indicating formation of condensed stacking structures with increasing rank. On the other hand, other XRD parameters, viz., the crystallite height ($L_c$) and thecrystallite diameter ($L_a$) were not correlated with the rank of the samples. Rock-Eval S2 programs depicted distinctive responses for the vitrains. While smooth curves were observed for the HvbA vitrain, the pyrograms showed unevenness and spikes for the Mvb and Lvb vitrains. We interpret these spikes orruggedness to be caused due to melt formation during pyrolysis of Lvb and Mvb vitrains, and concomitant gas/bubble-bursting. We back our results with distinctive observations from the Beld emission scanning electron microscope (FE-SEM) of the pyrolysis-residues of the vitrains. We interpret that the distinctive S2 signatures shown by coals can be useful in predicting their end usage.

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