Carbonisation of fir (Abies bornmulleriana) wood in an open pyrolysis system at 50-300 degrees C

Abstract

The aim of the present study was to investigate the carbonisation of a fir wood sample in an open pyrolysis system under a nitrogen atmosphere at temperatures ranging from 50 to 300 °C to contribute to the knowledge of artificial coalification. The sample used in this work was a bark-free fir (Abies bornmulleriana) sawdust sample obtained from Bolu forests (northwest Anatolia) in Turkey. The pyrolysis reactions were investigated isothermally in the temperature range of 50–300 °C and in times ranging from 1/2 to 50 h. Conversion of the wood increased with higher rates during the initial times and reached a steady state after approximately 35 h of heat treatment at all temperatures. The simultaneous increase in the amount of volatiles after 150 °C can be explained by the depolymerization of the network. Evolution of a coal-like pattern in the FTIR spectra of the carbonised wood could be observed by disappearance of bands due to cellulose, hemicellulose and lignin in the range of 1300–1000 cm−1 and appearance of two new bands at about 1250 cm−1 (asymmetric C---O---C stretching vibrations) and 1450 cm−1 (aliphatic C---H bending). The H/C ratio decreases too early before the end of the diagenetic stage and as the temperature of pyrolysis was increased a decrease in the O/C ratio was observed which corresponded to the dehydration and decarboxylation of the original material. The cross-link density continued to decrease in the carbonised material obtained until 100 °C and the cross-link density started to increase in the material formed at higher temperatures