Chemical Characteristics of Flue Gas Particulates: An Experimental Investigation

The present work aims at characterizing particulate matter (PM) of different size, emitted during biomass gasification in a drop tube furnace (DTF) at 1000 °C. The elemental composition was determined using X-ray fluorescence (XRF) and Electron Paramagnetic Resonance (EPR) analyses. Overall 19 elements were determined and the relative mass concentration of their oxides was identified as macro- (above 3%) and micro-concentration (below 3%). The elements Fe, Mn and S were found in each type of particulates, regardless of the used biomass and gasifying agent. The dominant macro component of char (cyclone particles >10 µm) was Ca (50.56–100% of the total CaO), followed by K, Fe, S, Mn and Cr. Only colza char contained significant portion of P and much lower Fe. The primary macro constituents of PM_10–2.5 were Fe, Mn and S. The volatile ash compounds K and Cl are typical constituents of the submicron sized ultrafine particles (UFP), when biomass from agricultural residue was gasified. This confirms the hypothesis that elements, having low boiling point significantly influence UFP formation through the nucleation. Two EPR spectra were obtained for the char samples: a broad signal with g ≈ 2.1–2.6, and a narrow sharp signal with g ≈ 2.002–2.003. The broad EPR signal was attributed to the paramagnetic metal ions Fe³⁺ and Mn²⁺, which was in agreement with the XRF analysis. The narrow signal was attributed to the appearance of soot particles.