Temperature resolved release of inorganic compounds from biomass

The release of inorganic compounds during the thermal conversion of solid biomass can cause severe operational problems in thermal power plants. To effectively reduce fine particle emissions and depositions, it is important to understand the release of problematic elements into the gas phase. This study presents a temperature-resolved analysis of the release of potassium, sodium, chlorine, sulfur, phosphorus, calcium, and magnesium from ten biomass samples. Conventional woody biofuels, alternative woody biofuels, and stalk-like biomass are analyzed in an electrothermal vaporization unit (ETV) which is connected directly to an inductively coupled plasma optical emission spectrometer (ICP-OES). The suppression of secondary gas-phase reactions in the given setup enables the isolated observation of each individual species' release pattern. The results from this experimental setup are compared to a range of release patterns found in the literature, with a particular focus on potassium. For the high heating rates applied in this setup, the potassium release starts at around 700 °C, with the majority being release between 1000 °C and 1400 °C. Since hardly any potassium is released together with chlorine and sulfur, the majority of it is released as KOH or elemental potassium. Overall, this work presents reproducible temperature-resolved release patterns of inorganic elements from various biogenic feedstocks in an inert atmosphere.