Thermal characterization and gasification kinetics of thrace-saray region coal

Yıldırım, Betül
In this thesis being up as-received and washed and dried, two different coal samples from Saray-Edirkoy field were experimented in order to determine effects of different variables as coal type, heating rate, gas flow rate, isothermal duration, gasifying medium, and final gasification temperature, on isothermal gasification profiles of the coal samples. In the scope of this study, heating rate was changed in the range of 20-50oC/min as 20, 30, 40 and 50oC/min whereas two different gas flow rate values as 60 ml/min and 100 ml/min were used throughout the experiments. Isothermal period was increased from 60 minutes to 120 minutes to determine increased waiting period effect on process at designated temperature of the reaction. Carbon dioxide (CO2) and dry air were used as gasifying agents whereas nitrogen (N2) gas was selected as the inert gas. To be in the range of 750-950oC, totally five different final temperature values were tested (750, 825, 850, 900 and 950oC) for calculation of activation energies of the coal samples. In the study, important parameters for thermal characterization of the samples as reaction intervals for different stages of the gasification process, weight changes occurred in these reaction intervals, peak temperatures where maximum mass losses of the specified intervals occur, and the ignition temperatures were determined from thermogravimetry/differential thermogravimetry (TG/DTG) curves by TA Universal Analysis software program. As a result, for carbon dioxide gasification experiments, three reaction regions were identified which were matched with moisture loss, volatile matter release and gasification steps. On the other hand, for some of the dry air gasification experiments, four reaction intervals were observed which were correlated with free moisture loss, devolatilization, combustion of light volatile matter and some part of the char, and gasification steps respectively. In kinetic analysis session, first order Arrhenius kinetic model was used as a result of which activation energies (Ea) of the samples were calculated under both carbon dioxide and dry air atmospheres as two different gasification environments. In both environments, washed and dried coal sample was found to be more reactive than as received coal. Moreover, activation energies of both samples were found to be lower under dry air atmosphere than those determined under carbon dioxide gas. Additionally, scanning electron microscope (SEM) and X ray diffraction analysis were conducted in the Middle East Technical University Central Laboratory for determination of the compositional and physical morphologies of the samples at pre- and post- pyrolysis and gasification conditions. With evaluation of SEM results, sequence increment and decrement of porosity was identified with consecutive pyrolysis and gasification reactions especially for carbon dioxide gasification experiments. Moreover, by qualitative SEM and XRD analysis, general information was obtained about mineral matter of the samples.


Comparative kinetic analysis of raw and cleaned coals
Ozbas, K.E.; Kök, Mustafa Verşan; Hicyilmaz, C. (2002-09-24)
In this research, thermogravimetry (TG/DTG) was used to determine the kinetic analysis of different coals and effect of cleaning process on kinetic parameters of raw and cleaned coal samples from Soma, Tuncbilek and Afsin Elbistan regions. Kinetic parameters of the samples were determined using Arrhenius and Coats and Redfern kinetic models and the results are discussed.
Thermal analysis applications in fossil fuel science - Literature survey
Kök, Mustafa Verşan (2002-01-01)
In this study, instances where thermal analysis techniques ( differential scanning calorimetry, thermogravimetry, differential thermal analysis, etc.) have been applied for fossil fuel characterisation and kinetics are reviewed. The scientific results presented clearly showed that thermal analysis is a well-established technique used in fossil fuel research area. The literature survey showed that thermal methods were important not only theoretically but also from a practical point of view.
Simultaneous thermogravimetry-calorimetry study on the combustion of coal samples: Effect of heating rate
Kök, Mustafa Verşan (2012-01-01)
Combustion characteristics of two different coal samples were investigated using power compensating type differential scanning calorimeter (DSC) and thermogravimetry (TG-DTG) at different heating rates (5, 10 and 15 degrees C/min). Differential scanning calorimeter (DSC) and thermogravimetry (TG-DTG) curves revealed two main reaction regions at each heating rate studied. Reaction regions, peak and burn-out temperatures, weight loss and heat of reactions of the samples were determined. Kinetic parameters of ...
Pyrolysis, combustion and gasification studies of different sized coal particles using TGA-MS
Jayaraman, Kandasamy; Kök, Mustafa Verşan; Gokalp, Iskender (2017-10-01)
In this research, thermogravimetric and mass-spectrometric (TG-MS) analysis and kinetics of different sized (60 mu m,800 mu m, and 3 mm) Saray (Turkish origin) coal is examined at various combustion temperature ranges. Experiments are performed at the heating rate of 40 degrees C/min in an argon atmosphere up to combustion/gasification temperatures (850-1150 degrees C), which, is close to the conditions of fluidized bed systems for high ash coal applications. The combustion tests are performed at isothermal...
Pyrolysis and Combustion Studies of Fossil Fuels by Thermal Analysis Methods Review
Kök, Mustafa Verşan (1995-02-01)
Instances where differential scanning calorimetry, thermogravimetry and differential thermal analysis have been applied to study the pyrolysis and combustion behaviour of fossil fuels (peat, lignite, bituminous coals, anthracite, oil shales, crude oils, lignite-oil mixtures, etc.) are reviewed. The literature survey showed that thermal methods were important not only theoretically but also from a practical point of view.
Citation Formats
B. Yıldırım, “Thermal characterization and gasification kinetics of thrace-saray region coal,” M.S. - Master of Science, Middle East Technical University, 2015.