Investigation of the effect of alkali metal sorbents on the release and capture of trace elements during combustion of straw

This work deals advanced information on the effect of alkali metal sorbents on the release and capture of trace elements, with special focus on potassium and sodium, during combustion of straw. Investigated sorbents were fly ash, bentonite, kaoline and bauxite. The lab-scale release and sorption experiments were done with pure straw and straw/sorbent mixtures at 1200 °C. The hot gas was analysed by Molecular Beam Mass Spectrometry. Species of interest were 36HCl+ (m/z = 36), 39K+ (m/z = 39), 64SO2+ (m/z = 64), and 74KCl+ (m/z = 74). The release of 36HCl+ and 39K+ as well as 74KCl+ showed a strong correlation which proofed a recently proposed capture mechanism. All sorbents lowered the released amount of alkali metal species significantly. Bentonite and fly ash showed the best capture performance for potassium.