Temperature changes and main gas release characteristics of Larix gmelinii plantations during smoldering in Daxing’anling Mountain region of Heilongjiang Province, northeastern China

  Objective  This paper simulates the smouldering combustion process, and discusses the characteristics of soil surface temperature and main emissions in order to provide scientific reference for smouldering combustion kinetics, spread mechanism and fire monitoring.

  Method  Taking the forest soil in the Larix gmelinii plantations of the Daxing’an Mountains as the research object, the temperature variation, main emissions and the effect of moisture content (20%, 30%, 40%) on emissions were analyzed by the results of smouldering furnace experiment.

  Result  The soil surface temperature firstly increased rapidly, then remained stable, and finally decreased rapidly until extinguished during the smouldering combustion process; according to the characteristics of soil surface temperature, the smouldering combustion was divided into four stages, i.e. ignition stage, rise stage, steady stage and extinguishing stage, and the modified combustion efficiency (MCE) of each smoldering stage was less than 0.75; the average concentration of CO₂ was 316.23 mg/m³, and the average concentration of CO was 101.25 mg/m³; in the smouldering combustion process, CO₂ emission was intermittent, but CO emission was continuous; combustion time had a significant effect on CO₂ and CO, but there was no correlation between CO₂ and CO; there was significant difference between the concentration of CO₂ under different moisture contents (P < 0.05), but there was no significant difference between the concentrations of CO (P > 0.05).

  Conclusion  The smouldering combustion shows a trend of conversion to flaming combustion after 14 h, according to the temperature and emission variation during the smouldering furnace experiment, but the combustion burnt out in the end for the decrease of combustible content; the concentration of CO₂ decreases with the increase of water content, resulting from the decrease of oxygen content and the increase of heat loss; smoldering combustion could maintain spread with moisture content of 20%−40%, so the concentration of CO has no significant difference.