Study on the thermodynamic characteristics of wood combustion in historical buildings

Abstract

Fire can cause devastating damage to ancient buildings; therefore, a theoretical basis regarding the stages of fire development and fire extinguishing studies in historical buildings is provided by studying the release patterns of combustion gas products from ancient building timbers. In this paper, TG-MS-FTIR experiments were employed to investigate the gas products and release patterns of ancient building wood during pyrolysis. Meanwhile, PY-GC/MS experiments were carried out in a helium atmosphere at temperatures to study the thermal cracking products of ancient building wood. From the experiments, it can be concluded that the values of the activation energy of ancient building wood range from 78.93395 to 209.8952 KJ/mol, with a maximum value at a conversion rate of 0.3 and a minimum value at a conversion rate of 0.9. The gasses produced during the pyrolysis of ancient construction wood were mainly CO, H2O, CO2, and CH4, and the mass spectrometry analysis showed that H2O had a double peak shape, CH4 had only one peak, and CO2 had two peaks. The overall trend of CO precipitation is that the amount of CO precipitation increases first and then decreases, and the amount of CO precipitation increases slowly at temperatures above 520 °C. The DTG maxima of ancient building timber differ considerably from those of fresh wood. This is due to the release of terpenes, which affect the intensity of their combustion. At the same time, the lignin content of ancient building timber is reduced, and the pyrolysis of lignin inhibits the pyrolysis of cellulose to a certain extent. There is a greater difference between ancient building timber and fresh wood at approximately 300 °C due to the decrease in lignin content.