Pyrolysis and thermogravimetric analysis of wood and its components

Abstract: The present study investigates the thermochemical conversion of spruce wood and its extracted components by thermogravimetric analysis. The extracted components are two pulps, three xylan-lignin samples and one lignin sample; they were produced by the kraft cooking method with different cooking times. The study involves characterization of the biomass through proximate analysis and pyrolysis. A qualitative comparison between the thermal behaviours of the extracted components and wood is also performed. The study showed that the thermal behaviour of the biomass was highly influenced by the content of cellulose and lignin in the samples. Compounds rich in cellulose produced large quantities of volatiles and had a higher rate of pyrolysis compared to compounds rich in lignin, which produced more char and had a slower rate of pyrolysis. It was also shown that, the amount of char is not solely depending on the amount of the lignin; the structure of the compound also plays a role. On the other hand, the original wood sample showed some deviations regarding the trends in volatile and char production and these deviations were attributed to component interactions. Both cellulose and lignin rich compounds had an increase in thermal stability with increasing cooking time. For the pulps the increase in thermal stability is believed to be caused by increase in crystallinity, while for the lignin rich samples is believed to be caused by the increase in lignin content and structural changes in the compounds. The results also show that although changes are introduced in the cooking process, the extracted component still retain properties exhibited by the source biomass.