Effect of low and high storage temperatures on headspace gas concentrations and physical properties of wood pellets

Abstract

Headspace gas concentrations and wood pellet properties were studied in sealed glass canisters at 5–40°C storage temperatures. CO2 and CO concentrations at 5, 10, 20 and 40°C at the end of 23–28 days of storage were 1600 and 200, 4700 and 1200, and 31 200 and 15 800 parts per million by volume (ppmv) respectively. Corresponding O2 concentration was about 19·49, 19·20, 18·0 and 2·07% respectively. Non-linear regression equations adequately described the gas concentrations in the storage container as a function of time. Safe level estimation functions developed were linear for O2 and logarithmic for CO and CO2 concentrations. Measured pellet properties moisture, length, diameter, unit, bulk and tapped density, durability, calorific value, ash content and percent fines were in the range of 4·6–5·02%, 14–15 mm, 6·4–6·5 mm, 1125–1175 kg m−3, 750–770 kg m−3, 825–840 kg m−3, 73–74%, 18·32–18·78 MJ kg−1, 0·65–0·74% and 0·13–0·15%. Durability values of pellets decreased by 13% at 40°C storage temperature and other properties changed marginally.