Thermal degradation, characterization and kinetic modeling of different particle size coal through TGA (original) (raw)
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Pyrolysis characteristics and kinetics of Indian low rank coal using thermogravimetric analysis
International Journal of Coal Science & Technology, 2019
The present research work deals with the thermogravimetric analysis (TGA) and kinetic analysis of three typical Indian low rank coals selected from Indian coal mines at various temperature ranges. Experiments were performed at four different heating rate (50, 100, 150, 200 K/min) for three typical Indian low rank coal samples in a nitrogen atmosphere from temperature range 30-950°C. The peak of temperature and mass loss for Indian low rank coal were evaluated. Current study also deals for the utilization and the behaviour of Indian low rank coal during the pyrolysis by using TGA. The activation energy for Indian low rank coal were calculated based on TGA data by using Friedman Method. Corresponding calculated mean value of activation energy for Indian low rank coal is found 49.132 kJ/mol. These experimental results help to explain and predict the behaviour of Indian low rank coal in practical applications.
Energy Sources, Part A: Recovery, Utilization, and Environmental Effects, 2019
Pyrolysis is a common stage of many coal utilization processes such as carbonization, gasification, combustion, and liquefaction. Char is the main product from slow pyrolysis of coal. Proximate analysis of Makarwal coal sample has ash contents of 34.61% and heating rate of 12,300 Btu/lb. CHNS analysis yields the elemental carbon of 43.41 % and sulfur amount of 58.041% which can be removed by further treatment process. Thermogravimetric analysis (TGA) study of Makarwal coal sample recognized that maximum decomposition takes place at 441ºC. The rate of reaction, rate constant and activation energy estimated from the kinetic study of slow pyrolysis are 7.55*10 −5 mol/cm 3. s, 0.001135/s and 0.045 kj/mol, respectively. Experiments were performed at different coal particles with size ranging from 0.5 to 0.2 mm and heating rate of 9-15ºC/min at temperature range of 300-700ºC under inert N 2 gas atmosphere. Char is the main product in this study which is maximum at 9ºC/min and temperature of 300ºC having conversion rate of 92%. The desired char products have 44.63% fixed carbon and HHV of 14,300 Btu/lb.
Energy, 2020
Five coal samples from different origins are characterized for their pyrolysis and combustion features using coupled thermogravimetry-mass spectrometry (TG-MS). The samples are heated at temperatures ranging from 25 to 900 C in air atmosphere under heating rates of 10, 20, and 30 C/min. The characteristic temperatures (initial, peak, burn out), reaction intervals, mass loss rate, ash residues, ignition and combustion performances, an ignition-combustion index and the reactivities of the coal samples are calculated and the associated heating rate effects are estimated. The less reactive coal exhibits higher peak temperature in conversion and low value of ignition index and reactivity. The reactivity of the coal samples varied in between 2.31 and 7.84 x10 2 (1/min). The main volatile and combustion products (H 2 , CH 4 , H 2 O, CO, CO 2 , C 6 H 6 , COS, SO 2) release for the corresponding TG and temperatures are estimated using online 3D measurements of MS based on their relative intensities and relevancy. Ozawa-Flynn-Wall (OFW) and Kissinger-Akahira-Sunose (KAS) type model free kinetic methods are applied to determine the activation energies of the coals which are exhibited in-between 44.6-75.1 kJ/mol and 50.5e96.6 kJ/mol using OFW and KAS methods respectively. The estimated kinetic constants are compared and found consistent with combustion performance parameters.
Kinetic study of Mongolian coals by thermal analysis
Mongolian Journal of Chemistry, 2018
Thermal analysis was used for the thermal characterization of the coal samples. The experiments were performed to study the pyrolysis and gasification kinetics of typical Mongolian brown coals. Low rank coals from Shivee ovoo, Ulaan ovoo, Aduun chuluun and Baganuur deposits have been investigated. Coal samples were heated in the thermogravimetric apparatus under argon at a temperature ranges of 25-1020ºC with heating rates of 10, 20, 30 and 40ºC/min. Thermogravimetry (TG) and derivative thermogravimetry (DTG) were performed to measure weight changes and rates of weight losses used for calculating the kinetic parameters. The activation energy (Ea) was calculated from the experimental results by using an Arrhenius type kinetic model.
Systematic Effects of Coal Rank and Type on the Kinetics of Coal Pyrolysis
Energy & Fuels, 2001
In this work, the global pyrolysis kinetics of a broad range of coals was studied by means of thermogravimetric experiments (heating rate ) 25°C/min). An Arrhenius-based deconvolution model was applied to the experimental DTG curves in order to obtain reliable kinetic parameters for the different DTG peaks. The model assumes that the weight loss rate ascribed to volatile release during primary and secondary pyrolysis is a result of the parallel occurrence of three pseudo-unimolecular nth-order reactions (peaks 1, 2, and 3). The kinetic results were expressed as a function of coal rank (0.43 e R r e 1.14%) and maceral composition in order to obtain reliable kinetic trends. By error minimization, an average apparent reaction order of 1.67 was found. The mass fractions corresponding to peaks 1, 2, and 3 were found to follow definite trends with rank and maceral composition. The temperature of maximum reactivity for peak 1 was almost coincident with that of the maximum overall reactivity and followed clear trends with coal rank and type. The activation energies of peaks 2 and 3 were found to be independent of coal type and clearly related to coal rank. The kinetic parameters (activation energy and preexponential factor) of the three peaks exhibited clear isokinetic effects. It is thought that the deviations of the obtained activation energies from those calculated by the isokinetic effect trends are a consequence of a narrow distribution of activation energies within each peak.
Application of chemometrics to study the kinetics of coal pyrolysis: A novel approach
Fuel, 2011
In present investigation, chemometric tools, principal component analysis (PCA) and Hierarchical clustering analysis (HCA) are used to get the linkage between the coal properties and kinetics of pyrolysis. Thermo gravimetric analysis (TGA) of 10 perhydrous Indian coals was done. Devolatilization of these coals showed five independent reactions. Kinetic parameters were calculated for individual reaction. Activation energy and weight loss of each reaction has been analyzed as a function of coal properties (moisture, volatile matter, ash, fixed carbon, carbon, hydrogen, nitrogen and sulfur). By applying chemometric, was extracted information about the linkage between activation energies of each reaction and coal properties. The mathematical treatment of data has provided conclusions on properties of coal and kinetic parameters.
Pyrolysis Study of Sarawak Coal Using Thermogravimetric Analysis
International Energy Journal, 2009
Pyrolysis of Sarawak coal was conducted using thermogravimetric (TG) study. Two coal samples, sub-bituminuous (Merit Pila coal) and bituminous (Silantek coal) were investigated within the temperature range of 300 900 oC at different heating rates of 10, 20, 30 and 40 oC min -1 , under inert nitrogen gas atmosphere. Differential thermogravimetric (DTG) data were analyzed using an Arrhenius type reaction model assuming a first-order reaction. Kinetic parameters, such as reactivity value, R T and activation energy, E a for the coals, were determined at different heating rates. Maximum rate temperatures and reactivity values for the coals were increased as the heating rates increased. The temperature at which maximum rate of decomposition occurred was found to be higher for bituminous coal than for lower rank coal. The activation energy E a for the coal is 37.40-38.92 kJ mol -1 , with sub-bituminous coal showing slightly higher E a than bituminous coal.
Energy Sources, Part A: Recovery, Utilization, and Environmental Effects, 2019
In the present investigation pyrolysis of high ash Indian coal is performed in N 2 ambiance using thermo-gravimetric analyzer under non-isothermal heating condition. The presence of various functional groups in low-grade high ash sub-bituminous coal is characterized by an FTIR analyzer. The absorbance spectra are categorized into four distinct zones, and functional groups are detected by the technique of curve-fitting. The evolved volatiles are analyzed by in-line Fourier Transform Infrared Spectrometry (FTIR) to identify the presence of various gaseous species (H 2 O, CO 2 , CO, COS) during thermal degradation of coal. Three different kinetic modelssingle reaction kinetic model (SRKM), single reaction and the distributed activation energy model (DAEM) are employed to estimate the activation energy and preexponential factor. Further, the single reaction model is extended with a multi-stage kinetic model (MKM) at various temperature ranges to evaluate the kinetic constants and is found to fit the experimental findings well. The evolution of CO 2 and CH 4 significantly depends upon the presence of the carboxylic group and aliphatic chains in low-grade coal. The quantification of evolved volatiles is also performed in Gas Chromatographic (GC) Analyzer, and the results confirm the presence of individual gaseous species as detected in the FTIR analyzer. The residual char obtained at a higher heating rate during pyrolysis exhibits a gradual rise in the BET surface area, resulting in the formation of more porous char.
Modeling and Experimental Investigations on the Pyrolysis of Large Coal Particles
Energy & Fuels, 2011
A fully transient and coupled kinetic, heat-transfer model is proposed to predict the pyrolysis behavior of a large coal particle. The model incorporates kinetics, internal convection because of volatile flow, conduction, external convection and radiation, variation in porosity and thermophysical properties, and changing particle size. The implicit Euler method is used to solve the kinetic model, while an implicit finite volume method (FVM) with a tridiagonal matrix algorithm (TDMA) is employed to solve the heat-transfer model equation. A general-purpose Fortran program is developed to solve the model equations. Experimental studies on mass loss and temperature profiles during pyrolysis are carried out for large coal particles in an isothermal mass-loss apparatus in the presence of nitrogen. Scanning electron microscope (SEM) images are used to explore the evolution of the structure of the coal/char. The swelling history is also investigated. The model predictions for coal temperature and fractional volatile loss are found in very fair agreement with the experimental results of the present authors, Fu et al. (Fu, W.; Zhang, Y.; Han, H.; Duan, Y. A study on devolatilization of large coal particles. Combust. Flame 1987, 70, 253À266), and Adesanys and Pham [Adesanya, B. A.; Pham, H. N. Mathematical modelling of devolatilization of a large coal particle in a convective environment. Fuel 1995, 74 (6), 896À902]. Finally, the effects of the temperature, particle swelling and shrinkage on the pyrolysis time, and loss of volatiles are analyzed through model simulation.