Simultaneous detection of K, KOH, and KCl in flames and released from biomass using photofragmentation TDLAS

Abstract

Gaseous potassium (K) species released from biomass during thermochemical conversion pose challenges to reactors and human health. Photofragmentation tunable diode laser absorption spectroscopy (PF-TDLAS) was used for simultaneous, high-dynamic range measurements of atomic K, potassium hydroxide (KOH) and potassium chloride (KCl) in flat flames seeded with KCl salt. An expression for the PF-TDLAS signal is presented and experimentally verified. Axial K species concentration profiles recorded at fuel-air equivalence ratios of 0.8 and 1.3 are compared to 2D axisymmetric reacting flow simulations. An overall good agreement is found, but KOH is over-predicted in simulations of fuel-rich flames at the expense of atomic K. Quantification of K species close to softwood and wheat straw particles converted in the flames is demonstrated.