TY - JOUR A1 - Berger, Anka A1 - Anca-Couce, A. A1 - Dieguez-Alonso, A. A1 - Zobel, N. A1 - Kienzl, N. A1 - Behrendt, F. T1 - Influence of heterogeneous secondary reactions during slow pyrolysis on char oxidation reactivity of woody biomass N2 - The influence of heterogeneous secondary reactions on char oxidation reactivity, which can take place during slow pyrolysis processes in a woody biomass particle, is analyzed in this study. To this end, the oxidative behavior of primary char produced in a thermobalance with initial wood masses of a few milligrams is compared to the behavior of char produced under conditions enhancing secondary reactions, i.e., large particle and bed sizes in fixed-bed reactors. The influence of the Maximum conversion temperature, heating rate, and catalytic effect of inorganics is also studied to compare the effect of each parameter. Results show that a significant reduction in reactivity takes place when char is produced under conditions enhancing These secondary reactions during pyrolysis. The effect is of similar order as the effect as a result of thermal annealing at 900 °C or the catalytic effect of alkali and alkaline earth metals. Therefore, the presence of heterogeneous secondary reactions during pyrolysis should be taken into account in studies addressing biomass char reactivity. Furthermore, it is shown that the reduction of reactivity as a result of secondary reactions is related to neither the loss of oxygen-containing functional groups nor the potential blocking of pores, specially micropores, resulting from the formation of this secondary char. The explanation may, therefore, lie on the deactivation or blocking of active sites by the secondary char. KW - Char conversion KW - Char reactivity KW - Pyrolysis KW - Woody biomass KW - Thermogravimetric analysis KW - TGA PY - 2017 DO - https://doi.org/10.1021/acs.energyfuels.6b02350 SN - 0887-0624 SN - 1520-5029 VL - 31 IS - 3 SP - 2335 EP - 2344 PB - ACS Publications AN - OPUS4-40189 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - JOUR A1 - Anca-Couce, A. A1 - Zobel, N. A1 - Berger, Anka A1 - Behrendt, F. T1 - Smouldering of pine wood: kinetics and reaction heats N2 - A kinetic model of smouldering of pine wood is determined by thermo-gravimetric analysis (TGA), describing the reactions of wood pyrolysis, wood oxidation and char oxidation. Thermo-gravimetric experiments were conducted with constant heating rates ranging from 2.5 to 10 K/min in atmospheres of pure nitrogen and mixtures of nitrogen and oxygen (with 20.5%, 8.2% and 4.3% O2). At first wood pyrolysis and char oxidation experiments are carried out in an independent way. Then smouldering experiments are conducted, which combine the two previous reactions with wood oxidation. Finally, the heats of the reactions are determined by differential scanning calorimetry (DSC). The results are discussed, compared with the literature and the derived kinetic model is presented, which includes five components: three pseudo-components of wood – representing roughly cellulose, hemi-cellulose and lignin – as well as char and ashes. KW - Smouldering KW - Kinetics KW - TGA KW - Biomass PY - 2012 DO - https://doi.org/10.1016/j.combustflame.2011.11.015 SN - 0010-2180 SN - 1556-2921 VL - 159 IS - 4 SP - 1708 EP - 1719 PB - Elsevier Inc. CY - New York, NY AN - OPUS4-25761 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - JOUR A1 - Anca-Couce, A. A1 - Berger, Anka A1 - Zobel, N. T1 - How to determine consistent biomass pyrolysis kinetics in a parallel reaction scheme N2 - This paper discusses a method for determining the kinetics of biomass pyrolysis based on comparing isoconversional methods, such as the Kissinger and KAS methods, and least squares fitting in a parallel reaction scheme with three pseudo-components roughly representing cellulose, hemicellulose and lignin. The activation energies of the different pseudo-components reported in the literature vary widely. This variation could be reduced if care were taken to determine the kinetics of biomass pyrolysis: First, the reference experiments with pure cellulose are reproduced to validate the thermogravimetric analysis. Then, experiments are performed and analyzed with different heating rates and isoconversional methods are employed to verify the reliability of the experiments and to avoid selecting inappropriate reaction models in a fitting routine. KW - Kinetics KW - Biomass KW - Pyrolysis KW - Isoconversional KW - Fitting PY - 2014 DO - https://doi.org/10.1016/j.fuel.2014.01.014 SN - 0016-2361 VL - 123 SP - 230 EP - 240 PB - Elsevier Ltd. CY - Amsterdam AN - OPUS4-31176 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER -