Introduction Coal is an extraordinarily complex and heterogeneous material whose physical and chemical properties are difficult to determine. Turkey possesses substantial coal reserves [1]. Data on the chemical composition and structure of coal samples are still limited, despite the need for such data on economic and environmen- tal grounds. New and effective analytical methods are thus necessary for the more efficient utilisation of such coal samples [2–4]. The combustion and pyrolysis processes taking place in fossil fuels have been studied [5–24]. Pyroly- sis is the initial step in most coal-conversion processes, such as combustion, gasification and liquefaction, and has a significant influence on all subsequent stages. Accurate descriptions of coal pyrolysis are help- ful in the effective utilisation of coal and also impor- tant in the development of new pollution-control strat- egies [9–12]. Pyrolysis products depend on various pa- rameters such as the type of coal, particle size of the sample, temperature, heating rate, time, pressure, sweep-gas velocity, and gas residence time [7–15, 25]. In recent years, the application of thermogravi- metry (TG), differential scanning calorimetry (DSC) and derivative thermogravimetry (DTG) to study the combustion and pyrolysis behaviour of fossil fuels has gained widening acceptance among research workers, because of the importance of the resulting data for both industry and for the economy [13–31]. This paper determines the kinetic parameters for the pyrolysis of Hazro coal. Coal particle sizes were examined to determine the frequency factors and ele- mental composition. Experimental Hazro coal from the Southeast Anatolia region of Tur- key was used in this study. The coal sample was pre- pared according to ASTM standards [7, 10, 19, 32, 33]. The coal sample was dried in a vacuum desiccators and then crushed by means of a jaw crusher (Retsch BB 1/A), then ground in a rotor- beater mill (Retsch SRZ). The resulting material was then divided into representative sub-samples using an analytic sample divider (Retsch PT2). Test sieving was employed for particle-size analysis, using a Retsch 3B test-sieving device fitted with Tyler-series sieves (0.053–3.36 mm). The sieve analysis of the coal sample is presented in Table 1. C, H, N and S analyses were performed using a Carlo Erba ele- ment-analysis instrument (model EA 1108). The tech- nique used for the determination of C, H, N and S is based on the quantitative ‘Dynamic Flash Combus- tion’ method [32, 33]; the technical specifications of the EA 1108 elemental analyser are given elsewhere 1388–6150/$20.00 Akadémiai Kiadó, Budapest, Hungary © 2005 Akadémiai Kiadó, Budapest Springer, Dordrecht, The Netherlands Journal of Thermal Analysis and Calorimetry, Vol. 81 (2005) 395–398 PYROLYSIS KINETICS AND CHEMICAL COMPOSITION OF HAZRO COAL ACCORDING TO THE PARTICLE SIZE M. Z. Duz 1* , Y. Tonbul 1 , A. Baysal 1 , O. Akba 1 , A. Saydut 2 and C. Hamamci 1 1 Department of Chemistry, Faculty of Science and Art, Dicle University, 21280 Diyarbakir, Turkey 2 Department of Mining Engineering, Faculty of Engineering and Architecture, Dicle University, 21280 Diyarbakir, Turkey The relationship between particle size and chemical composition of Hazro coal (origin: SE Anatolia, Turkey) has been examined by elemental analysis and by thermogravimetric pyrolysis. The chemical composition of the coal was determined by grinding sample particles physically and separating according to their size in mm by sieving. Particle size distribution of the coal and chemical composition of these fractions were given. The coal has been non-isothermally pyrolysed in a thermogravimetric analyser to determine the kinetic factors. Thermal gravimetric (TG/DTG) experiments were performed from ambient temperature to 800°C under a nitrogen atmosphere at heating rate 10 K min –1 with five different particle size ranges. Kinetic parameters of the samples were determined using a Coats and Redfern ki- netic model, assuming a first-order reaction. Depending on the particle size of the coal samples, the mean activation energy values var- ied between 49.1 and 84.6 kJ mol –1 . The results discussed indicate that activation energies increase as the particle size decreases. Keywords: coal, elemental analysis, kinetic analysis, particle size, pyrolysis, thermogravimetry * Author for correspondence: zahird@dicle.edu.tr