The N2-pyrolysis of low-rank Sulcis coal was investigated by thermogravimetric techniques (TG/DTG) in the temperature range ambient to 1000 C under dynamic heating conditions (50, 75, and 100 C min-1 heating rates). Little differences in the mass losses with heating rates were observed. From thermogravimetric analysis it was established that coal pyrolysis consisted of three main stages: water evaporation; devolatilization of thermally labile and more stable volatiles; and char formation. The evolved gas (EGA) by Fourier transform infrared spectrometry (FTIR) coupled to the thermobalance under 100 C min-1 heating rate was conducted for the identification of the gaseous species and their evolution profiles during coal thermal degradation. The temperatures of maximum rate of release of H2O, CO2, CO, COS, C2H4, as well volatile fragments originating from breaking of covalent bonds such as alkyl and ether groups, were in agreement with the temperature of maximum mass-loss rate around 466 C. Meanwhile the maximum releasing rates of SO2, CH4, and NH3 took place at 330, 575, and 690 C, respectively. An increase of CO emission intensity at 770 C was indicating in situ gasification with CO 2-bearing product of freshly formed char. The kinetic processing of non-isothermal TG data was performed by isoconversional method. In the coal conversion regions α = 5-40% the apparent activation energies were almost constant suggesting a single-step reaction path. The calculated average E value was 189 kJ mol-1. A kinetic compensation effect existed between E and ln A: the linear dependence provided an average pre-exponential factor A 0 value of 2 × 1011 min-1. With further increase of conversion degree a complex E dependence on α was evident as the coal thermal degradation process underwent a multi-step reactions. © 2013 Elsevier B.V. All rights reserved.
TG-FTIR and kinetics of devolatilization of Sulcis coal
Scaccia, S.
2013-01-01
Abstract
The N2-pyrolysis of low-rank Sulcis coal was investigated by thermogravimetric techniques (TG/DTG) in the temperature range ambient to 1000 C under dynamic heating conditions (50, 75, and 100 C min-1 heating rates). Little differences in the mass losses with heating rates were observed. From thermogravimetric analysis it was established that coal pyrolysis consisted of three main stages: water evaporation; devolatilization of thermally labile and more stable volatiles; and char formation. The evolved gas (EGA) by Fourier transform infrared spectrometry (FTIR) coupled to the thermobalance under 100 C min-1 heating rate was conducted for the identification of the gaseous species and their evolution profiles during coal thermal degradation. The temperatures of maximum rate of release of H2O, CO2, CO, COS, C2H4, as well volatile fragments originating from breaking of covalent bonds such as alkyl and ether groups, were in agreement with the temperature of maximum mass-loss rate around 466 C. Meanwhile the maximum releasing rates of SO2, CH4, and NH3 took place at 330, 575, and 690 C, respectively. An increase of CO emission intensity at 770 C was indicating in situ gasification with CO 2-bearing product of freshly formed char. The kinetic processing of non-isothermal TG data was performed by isoconversional method. In the coal conversion regions α = 5-40% the apparent activation energies were almost constant suggesting a single-step reaction path. The calculated average E value was 189 kJ mol-1. A kinetic compensation effect existed between E and ln A: the linear dependence provided an average pre-exponential factor A 0 value of 2 × 1011 min-1. With further increase of conversion degree a complex E dependence on α was evident as the coal thermal degradation process underwent a multi-step reactions. © 2013 Elsevier B.V. All rights reserved.I documenti in IRIS sono protetti da copyright e tutti i diritti sono riservati, salvo diversa indicazione.
