Investigation of Thermal Degradation of Wood at Varying Values of Oxygen

Abstract

Cellulose materials such as wood, cotton, linen, paper, and cane and also products of their mechanical and chemical processing are widely used in industry and transport related to combustible materials due to their ability to emit flammable gases and vapors at the time of their decomposition and to leave solid residue (charcoal) as end product of pyrolisis under normal conditions. The research is aimed at defining immediate data as to the processes occurring within the samples of the materials during their dynamic heating in the course of thermogravimetric studies. We studied pine wood sawdust in the atmosphere of both normal air and that containing lowered oxygen content due to additional nitrogen induction. Thermogravimetric study of the processes of thermal degradation under dynamic regime was conducted using Q-1500 D derivatograph in order to reveal the temperature range within which thermal degradation of the materials is the most intensive. The results of the study of the process of pine wood thermal degradation show that endothermic processes take place within the wood samples under research upon reaching temperature equal to 100 ºC, the former are accompanied with loss of the samples' weight. In addition the temperatures corresponding to the commencement and maximum rate of the degradation process served as characteristics of thermal behaviour of the studied gas-air mixtures. The temperatures at which weight loss of the samples reached were determined from the thermograms and stages of the decomposition processes as well as relative weight loss when heated to 800 ºC were estimated. Moreover, we calculated magnitudes of the activation energy for wood thermal decomposition at different oxygen content in the air-gas environment. Thus, comparative analysis of the thermograms of the thermal-oxidative wood degradation at different oxygen content evidences that as the latter lowers in the environment wood pyrolisis occurs more slowly and is accompanied with higher energy consumption. Activation energy for the wood at its thermal decomposition rises more than twice as oxygen content decreases.

Keywords

• wood
• thermal degradation of wood
• activation energy
• pyrolisis
• oxygen concentration at the time of wood composition