Potential for flammability of gases emitted from stored wood pellets

Previous measurements have shown that freshly made wood pellets continued to emit flammable gases such as CO, H2 and CH4 during storage and handling. The research reported in this paper examines whether the concentration of these emitted gases and the available oxygen within enclosed wood pellet spaces can reach flammable levels. Glass jars filled to 75% volume with pellets were sealed and placed in controlled environments at 25, 40 and 60°C for a period of 9 weeks. Each batch of the stored pellet had a moisture content of 4%, 9%, 15%, 35% or 50% (wet mass basis). The concentrations of carbon monoxide (CO), carbon dioxide (CO2), methane (CH4), oxygen (O2), nitrogen (N2) and hydrogen (H2) were determined using gas chromatography. The flammability of the gas mixtures in the container headspace was calculated using ISO 10156 Standard ‘Gases and gas mixtures—Determination of fire and oxidizing ability for selection of cylinder valve outlets.’ It was concluded that the composition of the gas mixture does not reach flammable concentrations under all experimental conditions.