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

Gaseous potassium (K) species released from biomass during thermochemicalconversion pose challenges to reactors and human health. Photofragmentation tunable diodelaser absorption spectroscopy (PF-TDLAS) was used for simultaneous, high-dynamic rangemeasurements of atomic K, potassium hydroxide (KOH) and potassium chloride (KCl) inflat flames seeded with KCl salt. An expression for the PF-TDLAS signal is presented andexperimentally verified. Axial K species concentration profiles recorded at fuel-air equivalenceratios of 0.8 and 1.3 are compared to 2D axisymmetric reacting flow simulations. An overallgood agreement is found, but KOH is over-predicted in simulations of fuel-rich flames at theexpense of atomic K. Quantification of K species close to softwood and wheat straw particlesconverted in the flames is demonstrated