• Ananya Saikia

      Articles written in Journal of Earth System Science

    • The chemical composition of tertiary Indian coal ash and its combustion behaviour – a statistical approach: Part 2

      Arpita Sharma Ananya Saikia Puja Khare D K Dutta B P Baruah

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      In Part 1 of the present investigation, 37 representative Eocene coal samples of Meghalaya, India were analyzed and their physico-chemical characteristics and the major oxides and minerals present in ash samples were studied for assessing the genesis of these coals. Various statistical tools were also applied to study their genesis. The datasets from Part 1 used in this investigation (Part 2) show the contribution of major oxides towards ash fusion temperatures (AFTs). The regression analysis of high temperature ash (HTA) composition and initial deformation temperature (IDT) show a definite increasing or decreasing trend, which has been used to determine the predictive indices for slagging, fouling, and abrasion propensities during combustion practices. The increase or decrease of IDT is influenced by the increase of Fe2O3, Al2O3, SiO2, and CaO, respectively. Detrital-authigenic index (DAI) calculated from the ash composition and its relation with AFT indicates Sialoferric nature of these coals. The correlation analysis, Principal Component Analysis (PCA), and Hierarchical Cluster Analysis (HCA) were used to study the possible fouling, slagging, and abrasion potentials in boilers during the coal combustion processes. A positive relationship between slagging and heating values of the coal has been found in this study.

    • Genesis of some tertiary Indian coals from the chemical composition of ash – a statistical approach: Part 1

      Arpita Sharma Ananya Saikia Puja Khare B P Baruah

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      In the present investigation, 37 numbers of high sulphur tertiary coal samples from Meghalaya, India have been studied on the basis of proximate and ash analysis. Various statistical tools like Bivariant Analysis, Principal Component Analysis (PCA) and Hierarchical Clustering Analysis (HCA), and also the geochemical indicators were applied to determine the dominant detrital or authigenic affinity of the ash forming elements in these coals. The genetic interpretation of coal as well as the coal ash has been carried out based on chemical compositions of high temperature ash (HTA) by using Detrital/Authigenic Index. X-Ray Diffraction (XRD) analysis was also carried out to study the mineralogy of the studied coal ashes. Both statistical tools and geochemical indicators have confirmed the detrital nature of these coals as well as the ash forming elements.

    • Thermogravimetric and model-free kinetic studies on CO2 gasification of low-quality, high-sulphur Indian coals

      Tonkeswar Das Ananya Saikia Banashree Mahanta Rahul Choudhury Binoy K Saikia

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      Coal gasification with CO$_2$ has emerged as a cleaner and more efficient way for the production of energy, and it offers the advantages of CO$_2$ mitigation policies through simultaneous CO$_2$ sequestration. In the present investigation, a feasibility study on the gasification of three low-quality, high-sulphur coals fromthe north-eastern region (NER) of India in a CO$_2$ atmosphere using thermogravimetric analysis (TGADTA) has been made in order to have a better understanding of the physical and chemical characteristics in the process of gasification of coal. Model-free kinetics was applied to determine the activation energies (E) and pre-exponential factors (A) of the CO$_2$ gasification process of the coals. Multivariate nonlinear regression analyses were performed to find out the formal mechanisms, kinetic model, and the corresponding kinetic triplets. The results revealed that coal gasification with CO$_2$ mainly occurs in the temperature range of 800◦–1400◦C and a maximum of at around 1100◦C. The reaction mechanisms responsible for CO$_2$ gasification of the coals were observed to be of the ‘nth order with autocatalysis (CnB)’ and ‘nth order (Fn) mechanism’. The activation energy of the CO$_2$ gasification was found to be in the range 129.07–146.81 kJ mol$^{−1}$.

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